Independent group design: definition and examples (2023)

The phrase "practice makes perfect" applies to many areas of life, including research and experiments. People naturally get better by experimenting and learning over and over again. However, performing the same tasks repeatedly can cause problems when analyzing the impact of the tests. Participants can get used to this type of test after performing it several times. Also, repeating the same thing can make them bored and tired, which can also affect the quality of the survey. One way to avoid these problems is to use an Independent Group Design (IGD).

  • We begin by examining the definition of independent group design and how experimental design: independent groups is commonly used in research.
  • Next we will look at some examples of independent group design in the context of psychological research.
  • Finally, the advantages of the independent group design and the limitations of the independent group design are also discussed.

Design definition for independent groups

One hypothetical study compared the results to see how one group (the sleep-deprived experimental group) compared to another (the rested control group) on amemoryCheck. Well, in this experimental design, different participants participated under different experimental conditions, i.e. H. the sleep-deprived group versus the well-rested group. And it is this feature that makes this study an independent group design.

The Independent Group Design (IGD) is an experimental design that uses different participants for each experimental condition. The researcher exposes different groups of participants to different experimental conditions.

The defining feature of this experimental design is that each group usesdifferent participants.

Experimental Design: Independent Groups

An experimental design is a research method that aims to test a hypothesis and ensure that research is conducted in a controlled and scientific manner; This leads to collecting representative data and drawing conclusions. If the researchers follow the appropriate steps and take the necessary actions, the results can be considered valid and reliable.

Remember that an experimental design measures the effect of the independent variable on the dependent variable.

In an independent group project, consider aExperimental-It is acheckedclusters. For the experimental group of subjects there are aManipulation of the independent variables.

To help you remember these terms, you can think of them as “cause” and “effect” values.

Öindependent variableacts as a 'cause' factor in the experiment. And themanipulated variableThat's itIndependentlyfrom othersvariables.

The value of the dependent variable is expected to depend on changes in the independent variable. It's the "effect" factor. And theVariable be hisMeasured.

Independent group design differs from repeated group design, which uses the same individuals on two or more different occasions for different experimental conditions. In projects with repeated actions, all participants perform each task.

Independent group design: definition and examples (1)Figure 1: Scientific research involves assigning participants to experimental conditions; an example is the independent group design.

Independent group design: examples from psychological research

Several study examples show what constitutes an independent group project. In the following text we present two.

Imagine a sleep study that looked at how different amounts of sleep affected people's reaction times. The hypothetical study recruitedtwo groups of ten different individuals.

While one group slept ten hours a night, the other group slept three; means that theindependent variablewill be the amount of sleep (the manipulated variable).

Ödependent variable(the measured variable) was the recorded reaction time.

the hypothesisLess sleep leads to slower reaction times
The independent variablehow much sleep groups 1 and 2 got
The dependent variablethe reaction time of people in groups 1 and 2

One group had ten hours of sleep, the other three, and different participants were tested in each condition, so the experimental design was an independent group design.

A second desk study used an independent group design to test the possible side effects of a prescription drug. The participants were divided into two groups, Group A and Group B.

Group A received the drug and Group B received a "placebo" drug (one withwithout active ingredients🇧🇷 Based on this research, we wouldn't expect any side effects in Group B, as the lack of active ingredients means the drug doesn't affect them.

In this case theindependent variableis the drug, and thedependent variableare the possible side effects of the drug.

the hypothesisDrug X causes side effect Y
The independent variablethe drug that people are taking
The dependent variablethe possible side effect

Group A is testing the drug and not taking the placebo. Group B does not test the drug and takes the placebo. Each group experiences different test conditions, so we can attribute differences in results to the specific manipulation of the independent variables, i.e., taking and not taking the drug. This is one of the many advantages of this experimental project compared to others.

There are three different types ofexperimental projects🇧🇷 The design of independent groups is part of it. Sometimes researchers use others; The type used depends on how the research method matches the participants to the experimental conditions.

The repeated measures design is used when the same participants are used in both experimental conditions. And a matched-pair design is used when participants are divided into groups, with each pair of groups being matched based on a key characteristic.

Advantages of the independent group design

There are advantages and disadvantages to using an independent group project to test a hypothesis.

However, investigators are sometimes required to use an independent group design because it may not be possible to test different participants in each condition.

Imagine a study testing the effectiveness of a review plan. When we test different participants who received the review plan and those who did not, the results may be due to participant variations.

Instead, a researcher can compare participants' test results before and after using the review plan. Because the study used the same participant in each condition, it is rated as aRepeated action design, which explains individual differences.

A key advantage of independent group projects is that they existno order effect.Because different participants are exposed to each condition, the order in which they are asked does not affect the outcome. Participants are more likely to respond. You can't practice and improve. You won't get tired or bored either.

In repeated measures designs, order effects such as the practice effect or the fatigue/boredom effect can affect the results of the experiment and therefore reduce the accuracy of the data.

Another advantage is that more participants are needed because everyone can only belong to one group, the results have greater external validity.

External validity refers to the extent to which the results of a study can be generalized to other people, situations, and environments.

The more people are involved, the higher the probability of a different representation and thus the external validity.

Ultimately, there is always the benefit of both.Time, effort and money savedbecause both groups of participants can be evaluated at the same time.

Independent Group Design Constraints

Since these are two different groups of people,more participants are needed.This can outweigh the benefit of testing both groups, since, for example, more equipment may be needed for more people, making the independent group design less cost-effective.

Attendeesvariablesexist.Because the groups of people are different, it is difficult to guarantee that the different results are due to the manipulated independent variable; The observed changes in DV may be due to the participantvariables.

Given the first example above showing the effect of reaction time on sleep, the general prediction is that those in the three-hour group will have slower reaction times.

But what if more than half of these subjects had participant-specific personal conditions that slowed their reaction time, regardless of how many hours they slept?

For example,poor diet or less dexterity/responsiveness in general, conditions never experienced before, while someone playing sports or video games may have better reaction times, affecting how results are recorded.

This is known asparticipating variable.

Another example might be that participants in a condition may be smarter (with higher IQ) than others.

Some variables are not always confusing because they are not that important (depends on whether they are relevant to the result or not). But if you care, this could result in invalid conclusive data.

So how can we reduce the probability of the variables involved?

The answer isspot checksAlthough this does not completely eliminate the problem, it does reduce the likelihood that participant variables will confound the results of the experiment.

Random selection means that each member of a population has an equal chance of being selected by random list generators on computers, or putting names in a trash can and pulling them out at random.

Random sampling is advantageous for independent group design experiments because of the unbiased selection. This increases the possibility of a more representative sample of participants and thus increases the external validity of the results.

Independent Group Design - Main Conclusions

  • The independent group design is an example of an experimental design. The main distinguishing feature of independent group projects is that individual participants are exposed to different experimental conditions.
  • We can think of one group as an experimental group and the other as a controlled group. The difference is the change in the independent variable, the "causative" factor of the experiment (eg, the number of hours the subjects slept).
  • The main advantages of the independent group design are that there are no ordering effects, there is greater external validity, and it saves time, effort, and money because both groups can be tested simultaneously.
  • There are also disadvantages to using independent group projects: more participants are needed (which is less cost-effective), and there is a chance that one participantvariableschange the validity of the results.
  • One way to overcome the main disadvantages is to try other ways to reduce costs and use random sampling to reduce bias.


What is an independent group design? ›

Independent groups design is an experimental design where different participants are used in each condition of the experiment.

What does independent design mean? ›

Independent measures design, also known as between-groups, is an experimental design where different participants are used in each condition of the independent variable. This means that each condition of the experiment includes a different group of participants.

What is the purpose of independent groups design? ›

The independent groups design is an experimental design whereby two groups are exposed to different experimental conditions. Usually half of the participants are assigned to the experimental group where they are exposed to a condition where the independent variable is manipulated.

What are the three major types of designs with two independent groups? ›

There are three different types of independent groups designs: – random groups designs, – matched groups designs, and – natural groups designs. Individuals are randomly assigned to the different conditions of the independent variable.

What is two independent group design? ›

A two-group design is when a researcher divides his or her subjects into two groups and then compares the results. The two groups usually consist of a control group, who does not get the treatment, and a treatment or experimental group, who does get the treatment.

Why is independent samples design good? ›

Advantage - Reduces demand characteristics: An independent samples design makes it less likely that participants will guess the hypothesis of the experiment. If participants complete the experiment twice, they might guess the purpose of the experiment, and change their behavior accordingly.

What is the main difference between independent groups and within groups designs? ›

In a within groups design they are exposed to all levels, in an independent groups design they are only exposed to one level. Participants are exposed to all the levels of an independent variable at roughly the same time, and a single attitudinal or behavioral preference is the dependent variable.

What is a strength of independent groups design? ›

A strength of the independent measures design is that because participants only take part in one condition participants are less likely to become border or practiced and therefore the experiment is more likely to measure natural real-life behaviour.

What is a dependent group design? ›

A within-subjects design is also called a dependent groups or repeated measures design because researchers compare related measures from the same participants between different conditions. All longitudinal studies use within-subjects designs to assess changes within the same individuals over time.

What are the advantages of independent groups? ›

  • No order effects.
  • Lower risk of demand characteristics.
  • Same tests/materials can be used.
Apr 7, 2014

What is an example of within groups design? ›

Another common example of a within-subjects design is medical testing, where researchers try to establish whether a drug is effective or whether a placebo effect is in order. The researchers, in the crudest form of the test, will give all of the participants the placebo, for a time, and monitor the results.

What are the differences between an independent groups design and a repeated measures design? ›

In an independent groups test, the subjects in the 2 groups or conditions (t test) or 3 groups, 4 groups, 5 groups ... (or 3 conditions, 4 conditions, ...) are different people. In a repeated measures case, the same subjects are being tested under different conditions. They are the same people.

What is an example of two independent samples? ›

For example to compare heights of males and females, we could take a random sample of 100 females and another random sample of 100 males. The result would be two samples which are independent of each other.

How do you know if an independent group? ›

How are dependent and independent samples different?
  • If the values in one sample affect the values in the other sample, then the samples are dependent.
  • If the values in one sample reveal no information about those of the other sample, then the samples are independent.

What are two independent samples? ›

The independent samples mean that the two samples cannot be from the same group of people and they cannot be related in any way. However, two-sample T-test can also be used for pairwise comparisons when the “two” samples represent the same items tested in different scenarios.

What do independent samples mean? ›

Independent sample

In independent samples (or unpaired sample), the values come from two or more different groups. For example, if the group of men and the group of women are asked about their income, independent samples exist. In this case, a person from one sample cannot be assigned to a person from the other sample.

What does it mean to have independent samples? ›

Two samples are independentif the sample values selected from one population are not related or somehow paired or matched with the sample values selected from the other population.

What are dependent and independent groups? ›

Two (or more) samples are called independent if the members chosen for one sample do not determine which individuals are chosen for a second sample. Two (or more) samples are called dependent if the members chosen for one sample automatically determine which members are to be included in the second sample.

What is the difference between independent and control group? ›

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.

Is independent groups design related or unrelated? ›

Research design

Data can be either related or unrelated. Related data is produced from repeated measures and matched pairs designs. Unrelated data is produced from independent groups designs.

What is a limitation of independent group design? ›

You need twice as many participants so it is time consuming. Individual differences or participant variables may make the comparisons unreliable, so you can use random allocation which may balance it out as everyone has an equal chance of being selected for each condition.

Why is independent groups better than repeated measures? ›

The advantage of this is that individual differences between participants are removed as a potential confounding variable. Repeated measures also requires fewer participants, as data from all conditions is from the same group of participants.

How does independent groups design reduce demand characteristics? ›

Independent groups and matched pairs designs are generally at lower risk, as participants will not perform more than one condition of the experiment, so will be less likely to look into the study's aims.

What is dependent with examples? ›

relying on someone or something else for aid, support, etc. conditioned or determined by something else; contingent: Our trip is dependent on the weather. subordinate; subject: a dependent territory.

What is independent dependent variable and control group? ›

Dependent Variable = What is measured or observed; the "data" collected in the experiment. Experimental Group = Those participants exposed to the independent variable. Control Group = Those participants treated just like the experimental group EXCEPT they are not.

What are the advantages and disadvantages of independent? ›

6 Pros and Cons of Being Independent
  • Pro #1: It usually means you can take of yourself. ...
  • Con #1: You're probably not good at asking for help. ...
  • Pro #2: You have an attitude that won't keep you down for long. ...
  • Con #2: You probably aren't aware of or accommodating of your weaknesses. ...
  • Pro #3: You're able to look out for others too.
Apr 18, 2015

What are two types of group design? ›

The two basic two-group designs are the pretest-posttest control group design and the posttest-only control group design, while variations may include covariance designs.

What is a independent control group? ›

Definition: Control Group

In a scientific experiment, an independent variable remains constant in the control group and changes in the treatment group. These groups help establish a cause-and-effect relationship between the dependent and the independent variable.

What is an example of an independent sample? ›

Independent sample

In independent samples (or unpaired sample), the values come from two or more different groups. For example, if the group of men and the group of women are asked about their income, independent samples exist. In this case, a person from one sample cannot be assigned to a person from the other sample.

What is the difference between dependent and independent group? ›

Two (or more) samples are called independent if the members chosen for one sample do not determine which individuals are chosen for a second sample. Two (or more) samples are called dependent if the members chosen for one sample automatically determine which members are to be included in the second sample.

What is an independent variable group? ›

The independent variable (IV) in psychology is the characteristic of an experiment that is manipulated or changed by researchers, not by other variables in the experiment. For example, in an experiment looking at the effects of studying on test scores, studying would be the independent variable.

What are the 4 design categories? ›

Our hope is that understanding the design landscape through these four, simple categories—Commercial Design, Responsible Design, Experimental Design, and Discursive Design—will help the profession, our "consumers," and ourselves better understand design activity and ultimately its potential in an increasingly complex ...

What are some examples of independent and dependent variables and control? ›

Example: a car going down different surfaces. Independent variable: the surface of the slope rug, bubble wrap and wood. Dependent variable: the time it takes for the car to go down the slope. Controlled variable: the height of the slope, the car, the unit of time e.g. minutes and the length of the slope.

What is the difference between controlled and independent? ›

Control variables are held constant or measured throughout a study for both control and experimental groups, while an independent variable varies between control and experimental groups.

What is a good example of a control group? ›

Example of a Control Group

Assume you want to test a new medication for ADHD. One group would receive the new medication and the other group would receive a pill that looks exactly the same as the one that the others received, but it would be a placebo. The group who takes the placebo would be the control group.


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