control setup vs experimental setup

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The Difference Between Control Group and Experimental Group

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• Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
• B.A., Physics and Mathematics, Hastings College

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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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 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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