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The Difference Between Control Group and Experimental Group

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In an experiment , data from an experimental group is compared with data from a control group. These two groups should be identical in every respect except one: the difference between a control group and an experimental group is that the independent variable is changed for the experimental group, but is held constant in the control group.

Key Takeaways: Control vs. Experimental Group

• The control group and experimental group are compared against each other in an experiment. The only difference between the two groups is that the independent variable is changed in the experimental group. The independent variable is "controlled", or held constant, in the control group.
• A single experiment may include multiple experimental groups, which may all be compared against the control group.
• The purpose of having a control is to rule out other factors which may influence the results of an experiment. Not all experiments include a control group, but those that do are called "controlled experiments."
• A placebo may also be used in an experiment. A placebo isn't a substitute for a control group because subjects exposed to a placebo may experience effects from the belief they are being tested; this itself is known as the placebo effect.

What Are Is an Experimental Group in Experiment Design?

An experimental group is a test sample or the group that receives an experimental procedure. This group is exposed to changes in the independent variable being tested. The values of the independent variable and the impact on the dependent variable are recorded. An experiment may include multiple experimental groups at one time.

A control group is a group separated from the rest of the experiment such that the independent variable being tested cannot influence the results. This isolates the independent variable's effects on the experiment and can help rule out alternative explanations of the experimental results.

While all experiments have an experimental group, not all experiments require a control group. Controls are extremely useful where the experimental conditions are complex and difficult to isolate. Experiments that use control groups are called controlled experiments .

A Simple Example of a Controlled Experiment

A simple example of a controlled experiment may be used to determine whether or not plants need to be watered to live. The control group would be plants that are not watered. The experimental group would consist of plants that receive water. A clever scientist would wonder whether too much watering might kill the plants and would set up several experimental groups, each receiving a different amount of water.

Sometimes setting up a controlled experiment can be confusing. For example, a scientist may wonder whether or not a species of bacteria needs oxygen in order to live. To test this, cultures of bacteria may be left in the air, while other cultures are placed in a sealed container of nitrogen (the most common component of air) or deoxygenated air (which likely contained extra carbon dioxide). Which container is the control? Which is the experimental group?

Control Groups and Placebos

The most common type of control group is one held at ordinary conditions so it doesn't experience a changing variable. For example, If you want to explore the effect of salt on plant growth, the control group would be a set of plants not exposed to salt, while the experimental group would receive the salt treatment. If you want to test whether the duration of light exposure affects fish reproduction, the control group would be exposed to a "normal" number of hours of light, while the duration would change for the experimental group.

Experiments involving human subjects can be much more complex. If you're testing whether a drug is effective or not, for example, members of a control group may expect they will not be unaffected. To prevent skewing the results, a placebo may be used. A placebo is a substance that doesn't contain an active therapeutic agent. If a control group takes a placebo, participants don't know whether they are being treated or not, so they have the same expectations as members of the experimental group.

However, there is also the placebo effect to consider. Here, the recipient of the placebo experiences an effect or improvement because she believes there should be an effect. Another concern with a placebo is that it's not always easy to formulate one that truly free of active ingredients. For example, if a sugar pill is given as a placebo, there's a chance the sugar will affect the outcome of the experiment.

Positive and Negative Controls

Positive and negative controls are two other types of control groups:

• Positive control groups are control groups in which the conditions guarantee a positive result. Positive control groups are effective to show the experiment is functioning as planned.
• Negative control groups are control groups in which conditions produce a negative outcome. Negative control groups help identify outside influences which may be present that were not unaccounted for, such as contaminants.
• Bailey, R. A. (2008). Design of Comparative Experiments . Cambridge University Press. ISBN 978-0-521-68357-9.
• Chaplin, S. (2006). "The placebo response: an important part of treatment". Prescriber : 16–22. doi: 10.1002/psb.344
• Hinkelmann, Klaus; Kempthorne, Oscar (2008). Design and Analysis of Experiments, Volume I: Introduction to Experimental Design (2nd ed.). Wiley. ISBN 978-0-471-72756-9.
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Why control an experiment?

John s torday.

1 Department of Pediatrics, Harbor‐UCLA Medical Center, Torrance, CA, USA

František Baluška

2 IZMB, University of Bonn, Bonn, Germany

Empirical research is based on observation and experimentation. Yet, experimental controls are essential for overcoming our sensory limits and generating reliable, unbiased and objective results.

We made a deliberate decision to become scientists and not philosophers, because science offers the opportunity to test ideas using the scientific method. And once we began our formal training as scientists, the greatest challenge beyond formulating a testable or refutable hypothesis was designing appropriate controls for an experiment. In theory, this seems trivial, but in practice, it is often difficult. But where and when did this concept of controlling an experiment start? It is largely attributed to Roger Bacon, who emphasized the use of artificial experiments to provide additional evidence for observations in his Novum Organum Scientiarum in 1620. Other philosophers took up the concept of empirical research: in 1877, Charles Peirce redefined the scientific method in The Fixation of Belief as the most efficient and reliable way to prove a hypothesis. In the 1930s, Karl Popper emphasized the necessity of refuting hypotheses in The Logic of Scientific Discoveries . While these influential works do not explicitly discuss controls as an integral part of experiments, their importance for generating solid and reliable results is nonetheless implicit.

… once we began our formal training as scientists, the greatest challenge beyond formulating a testable or refutable hypothesis was designing appropriate controls for an experiment.

But the scientific method based on experimentation and observation has come under criticism of late in light of the ever more complex problems faced in physics and biology. Chris Anderson, the editor of Wired Magazine, proposed that we should turn to statistical analysis, machine learning, and pattern recognition instead of creating and testing hypotheses, based on the Informatics credo that if you cannot answer the question, you need more data. However, this attitude subsumes that we already have enough data and that we just cannot make sense of it. This assumption is in direct conflict with David Bohm's thesis that there are two “Orders”, the Explicate and Implicate 1 . The Explicate Order is the way in which our subjective sensory systems perceive the world 2 . In contrast, Bohm's Implicate Order would represent the objective reality beyond our perception. This view—that we have only a subjective understanding of reality—dates back to Galileo Galilei who, in 1623, criticized the Aristotelian concept of absolute and objective qualities of our sensory perceptions 3 and to Plato's cave allegory that reality is only what our senses allow us to see.

The only way for systematically overcoming the limits of our sensory apparatus and to get a glimpse of the Implicate Order is through the scientific method, through hypothesis‐testing, controlled experimentation. Beyond the methodology, controlling an experiment is critically important to ensure that the observed results are not just random events; they help scientists to distinguish between the “signal” and the background “noise” that are inherent in natural and living systems. For example, the detection method for the recent discovery of gravitational waves used four‐dimensional reference points to factor out the background noise of the Cosmos. Controls also help to account for errors and variability in the experimental setup and measuring tools: The negative control of an enzyme assay, for instance, tests for any unrelated background signals from the assay or measurement. In short, controls are essential for the unbiased, objective observation and measurement of the dependent variable in response to the experimental setup.

The only way for systematically overcoming the limits of our sensory apparatus […] is through the Scientific Method, through hypothesis‐testing, controlled experimentation.

Nominally, both positive and negative controls are material and procedural; that is, they control for variability of the experimental materials and the procedure itself. But beyond the practical issues to avoid procedural and material artifacts, there is an underlying philosophical question. The need for experimental controls is a subliminal recognition of the relative and subjective nature of the Explicate Order. It requires controls as “reference points” in order to transcend it, and to approximate the Implicate Order.

This is similar to Peter Rowlands’ 4 dictum that everything in the Universe adds up to zero, the universal attractor in mathematics. Prior to the introduction of zero, mathematics lacked an absolute reference point similar to a negative or positive control in an experiment. The same is true of biology, where the cell is the reference point owing to its negative entropy: It appears as an attractor for the energy of its environment. Hence, there is a need for careful controls in biology: The homeostatic balance that is inherent to life varies during the course of an experiment and therefore must be precisely controlled to distinguish noise from signal and approximate the Implicate Order of life.

P  < 0.05 tacitly acknowledges the explicate order

Another example of the “subjectivity” of our perception is the level of accuracy we accept for differences between groups. For example, when we use statistical methods to determine if an observed difference between control and experimental groups is a random occurrence or a specific effect, we conventionally consider a p value of less than or equal to 5% as statistically significant; that is, there is a less than 0.05 probability that the effect is random. The efficacy of this arbitrary convention has been debated for decades; suffice to say that despite questioning the validity of that convention, a P value of < 0.05 reflects our acceptance of the subjectivity of our perception of reality.

… controls are essential for the unbiased, objective observation and measurement of the dependent variable in response to the experimental setup.

Thus, if we do away with hypothesis‐testing science in favor of informatics based on data and statistics—referring to Anderson's suggestion—it reflects our acceptance of the noise in the system. However, mere data analysis without any underlying hypothesis is tantamount to “garbage in‐garbage out”, in contrast to well‐controlled imaginative experiments to separate the wheat from the chaff. Albert Einstein was quoted as saying that imagination was more important than knowledge.

The ultimate purpose of the scientific method is to understand ourselves and our place in Nature. Conventionally, we subscribe to the Anthropic Principle, that we are “in” this Universe, whereas the Endosymbiosis Theory, advocated by Lynn Margulis, stipulates that we are “of” this Universe as a result of the assimilation of the physical environment. According to this theory, the organism endogenizes external factors to make them physiologically “useful”, such as iron as the core of the hemoglobin molecule, or ancient bacteria as mitochondria.

… there is a fundamental difference between knowing via believing and knowing based on empirical research.

By applying the developmental mechanism of cell–cell communication to phylogeny, we have revealed the interrelationships between cells and explained evolution from its origin as the unicellular state to multicellularity via cell–cell communication. The ultimate outcome of this research is that consciousness is the product of cellular processes and cell–cell communication in order to react to the environment and better anticipate future events 5 , 6 . Consciousness is an essential prerequisite for transcending the Explicate Order toward the Implicate Order via cellular sensory and cognitive systems that feed an ever‐expanding organismal knowledge about both the environment and itself.

It is here where the empirical approach to understanding nature comes in with its emphasis that knowledge comes only from sensual experience rather than innate ideas or traditions. In the context of the cell or higher systems, knowledge about the environment can only be gained by sensing and analyzing the environment. Empiricism is similar to an equation in which the variables and terms form a product, or a chemical reaction, or a biological process where the substrates, aka sensory data, form products, that is, knowledge. However, it requires another step—imagination, according to Albert Einstein—to transcend the Explicate Order in order to gain insight into the Implicate Order. Take for instance, Dmitri Ivanovich Mendeleev's Periodic Table of Elements: his brilliant insight was not just to use Atomic Number to organize it, but also to consider the chemical reactivities of the Elements by sorting them into columns. By introducing chemical reactivity to the Periodic Table, Mendeleev provided something like the “fourth wall” in Drama, which gives the audience an omniscient, god‐like perspective on what is happening on stage.

The capacity to transcend the subjective Explicate Order to approximate the objective Implicate Order is not unlike Eastern philosophies like Buddhism or Taoism, which were practiced long before the scientific method. An Indian philosopher once pointed out that the Hindus have known for 30,000 years that the Earth revolves around the sun, while the Europeans only realized this a few hundred years ago based on the work of Copernicus, Brahe, and Galileo. However, there is a fundamental difference between knowing via believing and knowing based on empirical research. A similar example is Aristotle's refusal to test whether a large stone would fall faster than a small one, as he knew the answer already 7 . Galileo eventually performed the experiment from the Leaning Tower in Pisa to demonstrate that the fall time of two objects is independent of their mass—which disproved Aristotle's theory of gravity that stipulated that objects fall at a speed proportional to their mass. Again, it demonstrates the power of empiricism and experimentation as formulated by Francis Bacon, John Locke, and others, over intuition and rationalizing.

Even if our scientific instruments provide us with objective data, we still need to apply our consciousness to evaluate and interpret such data.

Following the evolution from the unicellular state to multicellular organisms—and reverse‐engineering it to a minimal‐cell state—reveals that biologic diversity is an artifact of the Explicate Order. Indeed, the unicell seems to be the primary level of selection in the Implicate Order, as it remains proximate to the First Principles of Physiology, namely negative entropy (negentropy), chemiosmosis, and homeostasis. The first two principles are necessary for growth and proliferation, whereas the last reflects Newton's Third Law of Motion that every action has an equal and opposite reaction so as to maintain homeostasis.

All organisms interact with their surroundings and assimilate their experience as epigenetic marks. Such marks extend to the DNA of germ cells and thus change the phenotypic expression of the offspring. The offspring, in turn, interacts with the environment in response to such epigenetic modifications, giving rise to the concept of the phenotype as an agent that actively and purposefully interacts with its environment in order to adapt and survive. This concept of phenotype based on agency linked to the Explicate Order fundamentally differs from its conventional description as a mere set of biologic characteristics. Organisms’ capacities to anticipate future stress situations from past memories are obvious in simple animals such as nematodes, as well as in plants and bacteria 8 , suggesting that the subjective Explicate Order controls both organismal behavior and trans‐generational evolution.

That perspective offers insight to the nature of consciousness: not as a “mind” that is separate from a “body”, but as an endogenization of physical matter, which complies with the Laws of Nature. In other words, consciousness is the physiologic manifestation of endogenized physical surroundings, compartmentalized, and made essential for all organisms by forming the basis for their physiology. Endocytosis and endocytic/synaptic vesicles contribute to endogenization of cellular surroundings, allowing eukaryotic organisms to gain knowledge about the environment. This is true not only for neurons in brains, but also for all eukaryotic cells 5 .

Such a view of consciousness offers insight to our awareness of our physical surroundings as the basis for self‐referential self‐organization. But this is predicated on our capacity to “experiment” with our environment. The burgeoning idea that we are entering the Anthropocene, a man‐made world founded on subjective senses instead of Natural Laws, is a dangerous step away from our innate evolutionary arc. Relying on just our senses and emotions, without experimentation and controls to understand the Implicate Order behind reality, is not just an abandonment of the principles of the Enlightenment, but also endangers the planet and its diversity of life.

Further reading

Anderson C (2008) The End of Theory: the data deluge makes the scientific method obsolete. Wired (December 23, 2008)

Bacon F (1620, 2011) Novum Organum Scientiarum. Nabu Press

Baluška F, Gagliano M, Witzany G (2018) Memory and Learning in Plants. Springer Nature

Charlesworth AG, Seroussi U, Claycomb JM (2019) Next‐Gen learning: the C. elegans approach. Cell 177: 1674–1676

Eliezer Y, Deshe N, Hoch L, Iwanir S, Pritz CO, Zaslaver A (2019) A memory circuit for coping with impending adversity. Curr Biol 29: 1573–1583

Gagliano M, Renton M, Depczynski M, Mancuso S (2014) Experience teaches plants to learn faster and forget slower in environments where it matters. Oecologia 175: 63–72

Gagliano M, Vyazovskiy VV, Borbély AA, Grimonprez M, Depczynski M (2016) Learning by association in plants. Sci Rep 6: 38427

Katz M, Shaham S (2019) Learning and memory: mind over matter in C. elegans . Curr Biol 29: R365‐R367

Kováč L (2007) Information and knowledge in biology – time for reappraisal. Plant Signal Behav 2: 65–73

Kováč L (2008) Bioenergetics – a key to brain and mind. Commun Integr Biol 1: 114–122

Koshland DE Jr (1980) Bacterial chemotaxis in relation to neurobiology. Annu Rev Neurosci 3: 43–75

Lyon P (2015) The cognitive cell: bacterial behavior reconsidered. Front Microbiol 6: 264

Margulis L (2001) The conscious cell. Ann NY Acad Sci 929: 55–70

Maximillian N (2018) The Metaphysics of Science and Aim‐Oriented Empiricism. Springer: New York

Mazzocchi F (2015) Could Big Data be the end of theory in science? EMBO Rep 16: 1250–1255

Moore RS, Kaletsky R, Murphy CT (2019) Piwi/PRG‐1 argonaute and TGF‐β mediate transgenerational learned pathogenic avoidance. Cell 177: 1827–1841

Peirce CS (1877) The Fixation of Belief. Popular Science Monthly 12: 1–15

Pigliucci M (2009) The end of theory in science? EMBO Rep 10: 534

Popper K (1959) The Logic of Scientific Discovery. Routledge: London

Posner R, Toker IA, Antonova O, Star E, Anava S, Azmon E, Hendricks M, Bracha S, Gingold H, Rechavi O (2019) Neuronal small RNAs control behavior transgenerationally. Cell 177: 1814–1826

Russell B (1912) The Problems of Philosophy. Henry Holt and Company: New York

Scerri E (2006) The Periodic Table: It's Story and Significance. Oxford University Press, Oxford

Shapiro JA (2007) Bacteria are small but not stupid: cognition, natural genetic engineering and socio‐bacteriology. Stud Hist Philos Biol Biomed Sci 38: 807–818

Torday JS, Miller WB Jr (2016) Biologic relativity: who is the observer and what is observed? Prog Biophys Mol Biol 121: 29–34

Torday JS, Rehan VK (2017) Evolution, the Logic of Biology. Wiley: Hoboken

Torday JS, Miller WB Jr (2016) Phenotype as agent for epigenetic inheritance. Biology (Basel) 5: 30

Wasserstein RL, Lazar NA (2016) The ASA's statement on p‐values: context, process and purpose. Am Statist 70: 129–133

Yamada T, Yang Y, Valnegri P, Juric I, Abnousi A, Markwalter KH, Guthrie AN, Godec A, Oldenborg A, Hu M, Holy TE, Bonni A (2019) Sensory experience remodels genome architecture in neural circuit to drive motor learning. Nature 569: 708–713

Ladislav Kováč discussed the advantages and drawbacks of the inductive method for science and the logic of scientific discoveries 9 . Obviously, technological advances have enabled scientists to expand the borders of knowledge, and informatics allows us to objectively analyze ever larger data‐sets. It was the telescope that enabled Tycho Brahe, Johannes Kepler, and Galileo Galilei to make accurate observations and infer the motion of the planets. The microscope provided Robert Koch and Louis Pasteur insights into the microbial world and determines the nature of infectious diseases. Particle colliders now give us a glimpse into the birth of the Universe, while DNA sequencing and bioinformatics have enormously advanced biology's goal to understand the molecular basis of life.

However, Kováč also reminds us that Bayesian inferences and reasoning have serious drawbacks, as documented in the instructive example of Bertrand Russell's “inductivist turkey”, which collected large amounts of reproducible data each morning about feeding time. Based on these observations, the turkey correctly predicted the feeding time for the next morning—until Christmas Eve when the turkey's throat was cut 9 . In order to avoid the fate of the “inductivist turkey”, mankind should also rely on Popperian deductive science, namely formulating theories, concepts, and hypotheses, which are either confirmed or refuted via stringent experimentation and proper controls. Even if our scientific instruments provide us with objective data, we still need to apply our consciousness to evaluate and interpret such data. Moreover, before we start using our scientific instruments, we need to pose scientific questions. Therefore, as suggested by Albert Szent‐Györgyi, we need both Dionysian and Apollonian types of scientists 10 . Unfortunately, as was the case in Szent‐Györgyi's times, the Dionysians are still struggling to get proper support.

There have been pleas for reconciling philosophy and science, which parted ways owing to the rise of empiricism. This essay recognizes the centrality experiments and their controls for the advancement of scientific thought, and the attendant advance in philosophy needed to cope with many extant and emerging issues in science and society. We need a common “will” to do so. The rationale is provided herein, if only.

Acknowledgements

John Torday has been a recipient of NIH Grant HL055268. František Baluška is thankful to numerous colleagues for very stimulating discussions on topics analyzed in this article.

EMBO Reports (2019) 20 : e49110 [ PMC free article ] [ PubMed ] [ Google Scholar ]

Contributor Information

John S Torday, Email: ude.alcu@yadrotj .

František Baluška, Email: ed.nnob-inu@aksulab .

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What Is a Control Setup in Science?

A control setup in science uses the same conditions and the same equipment as the experimental setup; however, there are no variables tested in the control setup, as there are in the experimental setup. A control setup can include the use of a control group, which takes place when the experiment includes people.

The people in the control group act as a control set-up. They do not receive the factor or active medication that the people do in the experimental group, which acts as the experimental setup.

A controlled experiment can use a control group or a controlled setup, but is designed so that only one variable is manipulated at a time. This is necessary for the experiment to produce accurate results because if there are multiple variables then the scientists cannot know which variable produced which result.

The scientific method is used in the experimental process and in a controlled setup. The scientific method has several steps, which are: ask a question, do background research, construct a hypothesis, test the hypothesis by doing an experiment, analyze the data and draw a conclusion and communicate the results. The scientific method is the method by which all experiments are conducted and allows scientists to ask and answer scientific questions through observations and experiments.

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That actually explain what's on your next test, experimental setup, from class:, mathematical crystallography.

An experimental setup refers to the specific arrangement of equipment, materials, and procedures used to conduct an experiment in a controlled environment. This setup is crucial for obtaining accurate and reliable data, as it minimizes variables that could affect the results and ensures that the experiment can be repeated under the same conditions. The design of an experimental setup also influences the efficiency of data collection strategies and processing methods.

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5 Must Know Facts For Your Next Test

• The experimental setup must be designed to control for external factors that could skew results, ensuring a clear relationship between variables.
• Proper arrangement and calibration of instruments are key aspects of an effective experimental setup, as they contribute to measurement accuracy.
• Different types of experiments may require different setups, such as single-blind or double-blind designs, to reduce bias.
• Documentation of the experimental setup is essential for reproducibility, allowing other researchers to replicate the study under similar conditions.
• Data collection strategies such as sampling methods and observational techniques heavily rely on how well the experimental setup is structured.

Review Questions

• The design of an experimental setup directly impacts data collection strategies by determining how variables are controlled and measured. A well-structured setup minimizes external influences and allows for precise measurements, which enhances the reliability of data collected. For example, if control variables are not properly managed within the setup, it can lead to erroneous conclusions from the data obtained, making it vital for researchers to carefully consider their experimental design.
• Calibration is critical in creating an effective experimental setup because it ensures that all instruments used in the experiment provide accurate and consistent measurements. Without proper calibration, even slight inaccuracies can lead to significant errors in data analysis. This affects not only the reliability of results but also the overall validity of the conclusions drawn from the experiment, highlighting why researchers must prioritize calibration during the setup phase.
• Varying experimental setups can significantly impact result interpretation by introducing different biases or controlling different variables. For instance, a single-blind setup may prevent participant bias but not researcher bias, affecting how outcomes are analyzed. If multiple studies on a similar topic use diverse setups without standardization, comparisons become challenging and may lead to conflicting interpretations. Thus, understanding these differences is crucial for synthesizing knowledge across studies and ensuring that findings are robust and applicable.

Related terms

Control Variables : Factors in an experiment that are kept constant to ensure that any changes in the dependent variable are due to the manipulation of the independent variable.

Data Acquisition : The process of collecting, measuring, and analyzing data from an experiment, which is often influenced by the design of the experimental setup.

Calibration : The process of adjusting and standardizing equipment used in an experiment to ensure accurate measurements.

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Tackle Control Set-up Questions Like A Pro

Posted by Lim Zi Ai | Jul 14, 2016 | Experimental Techniques , Primary 5 Science , Primary 6 Science , Primary School Science Techniques | 0 |

Experiment-centric questions are increasingly common in primary school examination papers today.

There are typically six types of experiment-centric questions that can be tested:

• Relationship – What is the relationship between X and Y?
• Fair Test – How do we ensure a fair test?
• Reliability – How can the experiment be more reliable?
• Aim – What is the aim of the experiment?
• Conclusion – What can you conclude from the experiment?
• Control Set-up – What is the purpose of the control set-up?

I’m sure you’ve probably seen a variation of one of the above questions in your child’s examination paper.

Read Also Tackling Conclusion Type Questions FAQ: The Pique Lab – Experimental Techniques Masterclass The CUE Method To Tackle Data-Based Questions

Many students often struggle to structure their answers in a coherent & scientific manner, causing them to lose marks unnecessarily.

The good news is that we know what are the possible experiment-centric questions that can be tested!

We’re able to help your child prepare these answers ahead of their examinations & execute them when they see something similar. 🙂

Isn’t that amazing?

In our previous article, we discussed tackling conclusion-type questions , arguably one of the more challenging experiment-centric questions.

Today, we’ll be looking at how to tackle control set-up questions . It is often expressed in the following format:

What is the purpose of the control set-up?

For this particular question, students are often able to identify the changed variable and the measured variable in the question. The challenge lies in using the correctly identified variables to structure their answers properly.

As such, I would like to introduce a template answer to help your child with control set-up questions.

Thought Process

A control set-up is often needed to ensure that the experiment is valid & accurate. It serves as a baseline for the comparison of the results of the main experiment.

The control set-up will also rule out other environmental variables from affecting the results and eventually help to establish the conclusion of the experiment.

Ultimately, the control set-up is in place to ensure that the measured variable (dependent variable)  is affected only by the changed variable (independent variable)  and not any other variable in the experiment.

Template Answer

The purpose of preparing Set-up __ is to act as a control set-up to ensure that the _____________ (measured variable) is only caused by the ___________ (changed variable) and not any other variables in the experiment.

Final Answer

With reference to part (b) of the above question…

The purpose of preparing Set-up B is to act as a control set-up to ensure that the change observed in the limewater (if any) is only caused by the gas produced during decomposition and not any other variables in the experiment.

I hope that this article has shown you how to apply to correct template answer to easily tackle experiment-centric questions on control set-ups!

Over the past 13 years, Ms. Zi Ai has worked with primary and secondary students from a wide spectrum of backgrounds. She is highly proficient in helping her students navigate the thought processes and answering techniques required to excel in PSLE Science examination. As a Psychology graduate from the National University of Singapore, she actively seeks to use her knowledge to get her students to be intrinsically motivated to learn Science. Her secret lies in helping the child rediscover their interest for learning through her wide arsenal of humorous and inspiring teaching methods.

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• What Is a Controlled Experiment? | Definitions & Examples

What Is a Controlled Experiment? | Definitions & Examples

Published on April 19, 2021 by Pritha Bhandari . Revised on June 22, 2023.

In experiments , researchers manipulate independent variables to test their effects on dependent variables. In a controlled experiment , all variables other than the independent variable are controlled or held constant so they don’t influence the dependent variable.

Controlling variables can involve:

• holding variables at a constant or restricted level (e.g., keeping room temperature fixed).
• measuring variables to statistically control for them in your analyses.
• balancing variables across your experiment through randomization (e.g., using a random order of tasks).

Table of contents

Why does control matter in experiments, methods of control, problems with controlled experiments, other interesting articles, frequently asked questions about controlled experiments.

Control in experiments is critical for internal validity , which allows you to establish a cause-and-effect relationship between variables. Strong validity also helps you avoid research biases , particularly ones related to issues with generalizability (like sampling bias and selection bias .)

• Your independent variable is the color used in advertising.
• Your dependent variable is the price that participants are willing to pay for a standard fast food meal.

Extraneous variables are factors that you’re not interested in studying, but that can still influence the dependent variable. For strong internal validity, you need to remove their effects from your experiment.

• Design and description of the meal,
• Study environment (e.g., temperature or lighting),
• Participant’s frequency of buying fast food,
• Participant’s familiarity with the specific fast food brand,
• Participant’s socioeconomic status.

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You can control some variables by standardizing your data collection procedures. All participants should be tested in the same environment with identical materials. Only the independent variable (e.g., ad color) should be systematically changed between groups.

Other extraneous variables can be controlled through your sampling procedures . Ideally, you’ll select a sample that’s representative of your target population by using relevant inclusion and exclusion criteria (e.g., including participants from a specific income bracket, and not including participants with color blindness).

By measuring extraneous participant variables (e.g., age or gender) that may affect your experimental results, you can also include them in later analyses.

After gathering your participants, you’ll need to place them into groups to test different independent variable treatments. The types of groups and method of assigning participants to groups will help you implement control in your experiment.

Control groups

Controlled experiments require control groups . Control groups allow you to test a comparable treatment, no treatment, or a fake treatment (e.g., a placebo to control for a placebo effect ), and compare the outcome with your experimental treatment.

You can assess whether it’s your treatment specifically that caused the outcomes, or whether time or any other treatment might have resulted in the same effects.

To test the effect of colors in advertising, each participant is placed in one of two groups:

• A control group that’s presented with red advertisements for a fast food meal.
• An experimental group that’s presented with green advertisements for the same fast food meal.

Random assignment

To avoid systematic differences and selection bias between the participants in your control and treatment groups, you should use random assignment .

This helps ensure that any extraneous participant variables are evenly distributed, allowing for a valid comparison between groups .

Random assignment is a hallmark of a “true experiment”—it differentiates true experiments from quasi-experiments .

Masking (blinding)

Masking in experiments means hiding condition assignment from participants or researchers—or, in a double-blind study , from both. It’s often used in clinical studies that test new treatments or drugs and is critical for avoiding several types of research bias .

Sometimes, researchers may unintentionally encourage participants to behave in ways that support their hypotheses , leading to observer bias . In other cases, cues in the study environment may signal the goal of the experiment to participants and influence their responses. These are called demand characteristics . If participants behave a particular way due to awareness of being observed (called a Hawthorne effect ), your results could be invalidated.

Using masking means that participants don’t know whether they’re in the control group or the experimental group. This helps you control biases from participants or researchers that could influence your study results.

You use an online survey form to present the advertisements to participants, and you leave the room while each participant completes the survey on the computer so that you can’t tell which condition each participant was in.

Although controlled experiments are the strongest way to test causal relationships, they also involve some challenges.

Difficult to control all variables

Especially in research with human participants, it’s impossible to hold all extraneous variables constant, because every individual has different experiences that may influence their perception, attitudes, or behaviors.

But measuring or restricting extraneous variables allows you to limit their influence or statistically control for them in your study.

Risk of low external validity

Controlled experiments have disadvantages when it comes to external validity —the extent to which your results can be generalized to broad populations and settings.

The more controlled your experiment is, the less it resembles real world contexts. That makes it harder to apply your findings outside of a controlled setting.

There’s always a tradeoff between internal and external validity . It’s important to consider your research aims when deciding whether to prioritize control or generalizability in your experiment.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

• Student’s  t -distribution
• Normal distribution
• Null and Alternative Hypotheses
• Chi square tests
• Confidence interval
• Quartiles & Quantiles
• Cluster sampling
• Stratified sampling
• Data cleansing
• Reproducibility vs Replicability
• Peer review
• Prospective cohort study

Research bias

• Implicit bias
• Cognitive bias
• Placebo effect
• Hawthorne effect
• Hindsight bias
• Affect heuristic
• Social desirability bias

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In a controlled experiment , all extraneous variables are held constant so that they can’t influence the results. Controlled experiments require:

• A control group that receives a standard treatment, a fake treatment, or no treatment.
• Random assignment of participants to ensure the groups are equivalent.

Depending on your study topic, there are various other methods of controlling variables .

An experimental group, also known as a treatment group, receives the treatment whose effect researchers wish to study, whereas a control group does not. They should be identical in all other ways.

Experimental design means planning a set of procedures to investigate a relationship between variables . To design a controlled experiment, you need:

• A testable hypothesis
• At least one independent variable that can be precisely manipulated
• At least one dependent variable that can be precisely measured

When designing the experiment, you decide:

• How you will manipulate the variable(s)
• How you will control for any potential confounding variables
• How many subjects or samples will be included in the study
• How subjects will be assigned to treatment levels

Experimental design is essential to the internal and external validity of your experiment.

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HOW TO TACKLE CONTROL SET-UP QUESTIONS

August 19, 2019 • Control Set-up • PSLE Science Answering Techniques

Control Set-up   :  Experimental-based Questions

Experimental-based questions are regularly tested in Primary School Science examinations.  In this article I will share with you three question samples on how to tackle questions involving control set-ups by using " 3C " method ( C ontrol -C ompare -C onfirm ) .

(i)   What is a Control Set-up? 

• An experimental set-up which is used for   comparison   in order to   confirm  the conclusion   of an experiment.
• An experimental set-up to show that the results obtained and observations made are only due to material tested and not other external factors. 

(ii)   Control Set-up Question is often expressed in the following format:

• Variant 1: Why is there a need for set-up B?
• Variant 2: Why is there a need for a control set-up?
• Variant 3: Draw and label a control set-up for the experiment.

(iii)   How to answer Variant 1, 2 and 3 Questions?

• Variant 1 : It acts as a control set-up to compare and confirm that the (Measured variable / Dependent variable) is only due to the (Changed variable / Independent variable) and not due to other variables in the experiment. 
• Variant 2   :  It is used t o   compare   and   confirm   that the   (Measured variable / Dependent variable)   is only due to the   (Changed variable / Independent variable)   and not due to other variables in the experiment. 
• Variant 3   :  To draw the control set-up is to  change/remove  the  (Changed variable / Independent variable) in the experimental set-up so as to prove that any change in result is only due to the (Changed variable / independent variable) and not because of other variables in the experiment. 

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Control Set-up: Acing Experiment-Based Questions in PSLE Science

This is the last of 5 articles on experiment-based questions in PSLE Science . Experimental-based questions are regularly tested in Science exam papers and it is important that students have mastery over the concepts tested.

The focus for today’s article is on control set-ups, another question type dreaded by students. They either do not understand the purpose of a control set-up or do not know how to draw a control set-up. Here, I will give you two specific examples on how to tackle questions involving control set-ups.

Purpose of a Control Set-up

• It is used for comparison in order to verify the conclusion of an experiment.
• To ensure that the measured variable (dependent variable) is affected only by the changed variable (independent variable) and not any other (control) variables in the experiment.

Scientist Strange carried out an experiment as shown below. He left both set-ups in a warm and dark cupboard for two days. He observed that the seeds in Set-up X germinated and the limewater turned cloudy while the limewater in Set-up Y remained clear.

What is the aim of the experiment and purpose of having Set-up Y?

• The only changed variable (independent variable) → presence of seeds
• Measured variable (dependent variable) → if carbon dioxide was given out by plant
• Control variable → all other variables in the experiment like size of beakers, amount of limewater, presence of rubber stoppers in both beakers, same location where experiment was carried out, etc.
• Since the aim of an experiment is related to the independent and dependent variable, the aim of the experiment is to find out if germinating seeds give out carbon dioxide .
• Purpose of Set-up Y → A control set-up to confirm that carbon dioxide was given out by the germinating seeds .

How to Draw the Control Set-up for an Experiment?

A good way to know how to draw the control set-up is to change the independent variable in the control set-up so as to prove that any change in result is only due to the independent variable and not because of other control variables .

This concludes the last of 5 articles on Experiment-Based Questions that are tested in school examinations and PSLE Science paper. With a subscription to OwlSmart , students get access over 200 experiment-based questions for PSLE Science with concise explanations. Students who practised more on these questions have shown to have a higher level of confidence in tackling them in the PSLE.

We wish you all the best in the coming P6 preliminary examinations and PSLE papers!

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Experimental Setup

• First Online: 25 July 2022

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• Cheng-An Chen 2  

Part of the book series: Springer Theses ((Springer Theses))

In this chapter, we introduce the main setup of our experimental apparatus. We began our quantum gas project in 2016. The general design idea of the experiment is to build a versatile yet compact quantum gas machine with great efficiency and extensive flexibility. The setup approximately includes four parts: lasers, electronic devices, vacuum chamber, and computer programs: of which we are proud to design and build most parts on our own. The details about a recent upgrade and the full capability of our quantum gas machine will be further elaborated in Chap. 7 .

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Chen, CA. (2022). Experimental Setup. In: Probing Non-Equilibrium Dynamics in Two-Dimensional Quantum Gases. Springer Theses. Springer, Cham. https://doi.org/10.1007/978-3-031-13355-8_2

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