Select your language

Suggested languages for you:
Log In Start studying!
StudySmarter - The all-in-one study app.
4.8 • +11k Ratings
More than 3 Million Downloads
Free
|
|

All-in-one learning app

  • Flashcards
  • NotesNotes
  • ExplanationsExplanations
  • Study Planner
  • Textbook solutions
Start studying

Experimental Designs

Save Save
Print Print
Edit Edit
Sign up to use all features for free. Sign up now
Experimental Designs

In previous articles, we discussed how to organise your ideal experiment down to the last detail, such as objectives, hypotheses, sampling methods, pilots, and variables. In this one, we're getting down to business the experimental designs.

Experimental design is the method in psychology by which participants (p) are assigned to different groups/conditions of an experiment. There are four types of experimental design: independent measurements, repeated measures, matched pairs, and quasi-experimental designs.

Independent measures experimental research design

The independent measures design is an experimental design in which different p’s are used to test each condition of the independent variable (IV). This experimental design is also known as the between-subjects design. Participants are randomly assigned to experimental groups, i.e., they are assigned to a condition under which they will be studied/observed.

An example of a research scenario using an independent measures design is as follows: ‘A study recruited 20 participants, 10 of whom slept 4 hours and 10 other different p’s slept 12 hours. These P’s were randomly assigned to their groups and took the same measures to assess attention span (only the IV differed the number of hours slept).

Advantages and disadvantages of independent group designs

Experimental Designs Advantages and disadvantages of independent measure experimental design StudySmarter

Advantages and disadvantages of using an independent measure experimental design, Manreet Thind, StudySmarter Originals

Repeated measures experimental research design

In a repeated measures design, p’s are assessed in each IV condition. Therefore, the data obtained for each IV condition come from the same participants. This experimental design is also referred to as a within-subjects design.

This experimental design may be considered problematic due to order effects, i.e., when the order of the presented conditions affects p’s performance. For example, p’s may perform better in the second condition because they know how to perform (practise effect) or may not perform as well due to fatigue (fatigue effect). Counterbalancing methods are used to counteract this. Half of the p’s complete the first condition first, and the others satisfy the second condition. In this way, it is possible to determine whether sequence effects influence the results.

An example of a research scenario using a repeated measures design is to investigate differences in depression scores before and after cognitive behavioural therapy.

Advantages and disadvantages of repeated measures design

Experimental Designs Advantages and disadvantages of repeated measure experimental design StudySmarter

Advantages and disadvantages of using a repeated measure experimental design, Manreet Thind, StudySmarter Originals

Matched-pairs experimental research design

In a matched-pairs design, p’s are paired concerning specific characteristics such as age, ethnicity, or education level. Each individual in the matched pair is randomly assigned to an experimental or control group.

An example of a study using a matched-pairs design is when 50 participants were recruited. The p’s were paired by age and gender, e.g., two males aged 21, two males aged 22, two females aged 21, two females aged 22, etc. These pairs were randomly assigned to the control group (standard diet) and the experimental group (keto diet) to measure weight loss.

Advantages and disadvantages of matched-pairs designs

Experimental Designs Advantages and disadvantages of matched-pairs experimental design StudySmarter

Advantages and disadvantages of using a matched-pairs experimental design, Manreet Thind, StudySmarter Originals

Quasi-experimental research design

The quasi-experimental design is similar to the independent measures design, except that p’s are not randomly assigned to a treatment or control group. Therefore, this method tests different p’s at each level of the IV. This method is typically used in psychological research to determine the effectiveness of an existing treatment/intervention.

Comparing the effectiveness of CBT in ‘healthy’ p’s and people with schizophrenia: as p’s with schizophrenia cannot be in the control group, we must use the quasi-experimental design as this research design does not allow random assignment to control and experimental groups.

Advantages and disadvantages of quasi-experimental designs

Experimental designs Advantages and disadvantages of quasi-experimental design StudySmarter

Advantages and disadvantages of using a quasi-experimental design, Manreet Thind, StudySmarter Originals

Experimental Designs - Key takeaways

  • An experimental design is a method by which p’s are assigned to various groups/conditions of an experiment.
  • There are four types of experimental designs: independent measures, repeated measures, matched pairs, and quasi-experimental designs.
  • The experimental design used is determined by the characteristics of the sample selected/assigned.
  • Independent measures and quasi-experimental designs are similar experimental designs but differ in sampling methods (i.e., random sampling of groups or fixed groups).
  • Random sampling and order effects are essential factors that researchers should consider when selecting and implementing experimental designs.

Frequently Asked Questions about Experimental Designs

Experimental design is the method in psychology by which participants (p) are assigned to different groups/conditions of an experiment.

To identify an appropriate experimental design, we must define variables and hypotheses. We can then choose a suitable experimental design based on: 

  • Whether participants can be randomly allocated to control or experimental groups. 
  • If the same participants should be tested on each IV condition or if different participants should be used.
  • If participants should be matched based on key characteristics to understand more about the proposed hypotheses.

The quasi-experimental design involves different participants being tested on each condition of the independent variable (IV). Participants are not randomly assigned to control and experimental groups for this design method.

An example of an experimental design is matched pairs design. This is when participants are paired in terms of specific characteristics such as age or ethnicity. Each individual of the matched pair is randomly assigned to an experimental or control group. An example of research that uses a matched-pair design is research that has recruited 50 participants that were paired in terms of age and gender, such as two males aged 21, two males aged 22, two females aged 21, two females aged 22, etc. These pairs were randomly assigned to the control group (standard diet) and the experimental group (keto diet) to measure weight loss.

Four types of experimental designs are: independent measures, repeated measures, matched pairs and quasi-experimental designs.

Final Experimental Designs Quiz

Question

What is an experimental design?

Show answer

Answer

Experimental design is a method used to allocate participants to different groups/ conditions of an experiment.

Show question

Question

What are four examples of experimental designs?

Show answer

Answer

The four experimental designs are independent measures, repeated measures, matched-pairs, and quasi-experimental designs.

Show question

Question

What is an independent measures design?

Show answer

Answer

The independent measures design is an experimental design in which different participants are used to test each condition of the independent variable. 

Show question

Question

What is a repeated measures design?

Show answer

Answer

A repeated measures design is when participants are assessed in all of the independent variable levels. Therefore, data obtained for each condition of the independent variable are taken from the same participants.

Show question

Question

What is a matched-pairs design? 

Show answer

Answer

Matched pairs design is when participants are paired in terms of specific characteristics such as age, ethnicity, or education level. Each individual of the matched pair is randomly assigned to the experimental or control group.

Show question

Question

What is a quasi-experimental design?

Show answer

Answer

This method involves different participants being tested on each independent variable level. This is usually used in psychology research to determine the effectiveness of pre-existing treatment/interventions. As a result, participants allocation into experimental and control groups is fixed. 

Show question

Question

For the following research scenario, ‘an investigation to identify if Clozapine (medication) is an effective drug to minimise symptoms of schizophrenia’, which experimental design would be appropriate to use and why?

Show answer

Answer

A quasi-experimental design would be appropriate because it can compare schizophrenia patients taking Clozapine (experimental group) and patients with schizophrenia using a different drug. This allows the researcher to identify if Clozapine or another drug is better at minimising symptoms of schizophrenia in the recruited sample. This design is required, as ethically, researchers cannot change patients medication because it may cause physical and/or psychological harm to participants.

Show question

Question

How do independent group designs and quasi-experimental designs differ?

Show answer

Answer

Independent measures design and quasi-experimental designs are similar experimental designs. However, they differ in terms of sampling methods. For instance, independent group designs use random sampling, whereas group allocation is fixed in quasi-experimental designs. 

Show question

Question

What is an advantage of using a repeated measure design over using independent measures experimental design?

Show answer

Answer

An advantage of using a repeated measures design instead of an independent design is that it is a more statistically robust design, accounting for individual differences. This can increase the reliability and validity of findings.

Show question

Question

What are the advantages and disadvantages of using a matched-pairs experimental design?

Show answer

Answer

The advantage of using a matched-pairs design is that it accounts for individual differences as participants are matched according to key characteristics such as age, ethnicity. This limits confounding variables, and this design is not affected by order effects. This design also uses random sampling techniques, increasing the reliability and validity of results. However, the disadvantages are that it is challenging to match participants, and the recruitment of participants can be time-consuming.

Show question

Question

What is counterbalancing and its purpose? 

Show answer

Answer

Counterbalancing is when the researcher changes the order that measures are presented to participants to reduce order effects. Order effects are when the order of measures presented influences participants performance. There are different order effects, such as the fatigue effect and practice effect. These can lower the validity of findings if they have not been combated with counterbalancing techniques.

Show question

Question

Which research designs have random sampling implications?

Show answer

Answer

Independent measures and quasi-experimental designs cannot use random sampling techniques.

Show question

Question

What is a repeated measures design?

Show answer

Answer

In the repeated measures, all participants experience all levels of IVs.

Show question

Question

Why are repeated measures criticised for having order effects?

Show answer

Answer

One of the major limitations of repeated measures is order effects. Order effects mean that tasks completed in one condition may have an effect on task performance in another condition.

Show question

Question

Why are repeated measures praised as cost-effective?

Show answer

Answer

Repeated measures design has great economic benefits as this design only requires half the number of participants with independent groups and matched pairs design. This is a tremendous economic benefit to the researchers as they will spend less time and resources to recruit participants.

Show question

Question

Why are repeated measures praised for having high validity?

Show answer

Answer

Participant variables are controlled because the same participants take part in both conditions. Participant variables are extraneous variables related to the individual characteristics of each participant and may influence their response. The same participants participate in each condition in a repeated measures design, so extraneous participant variables such as individual differences can be eliminated.

Show question

Question

Why are repeated measures criticised for having demand characteristics?

Show answer

Answer

The first test could induce demand characteristics because it allows participants to guess the target of the survey when it is repeated in the second test. There is a risk that participants will change some aspect of their behaviour in response to knowing the research hypothesis.

Show question

Question

How can research deal with the order effects?

Show answer

Answer

Counterbalancing is an experimental technique used to overcome order effects. Counterbalancing ensures each condition is tested equally first or second.

Show question

Question

How can research deal with the demand characteristics?

Show answer

Answer

A cover story about the purpose of the test can prevent participants from guessing the research hypothesis. The cover story should be plausible but false. Researchers communicate this statement to participants to prevent the true hypothesis from being revealed. Such deception can be practised when the knowledge of the experiment's true purpose can influence the participant's behaviour in the study. In this way, deception can allow the researcher to control demand characteristics and ensure better validity.

Show question

Question

What is a matched pairs design?

Show answer

Answer

Participants are paired up based on a specific trait or variables relevant to the study and then split into different conditions in the matched pairs design.

Show question

Question

Why don't matched pairs experiments have any issues with order effects?

Show answer

Answer

Matched pairs experiments don't have issues with order effects because all participants are only tested once in matched pairs. No practice effect or boredom effect will occur.

Show question

Question

Why is matched pairs design criticised as having low cost-effectiveness?

Show answer

Answer

Matched pairs design has a lower economic benefit as it requires more participants. Also, extra data must check the participants in pairs according to the relevant variables.

Show question

Question

Why is matched pairs design praised for having reduced demand characteristics?

Show answer

Answer

Matched pairs experiments don't have issues with demand characteristics. This is because participants are only tested once in matched pairs. They are less likely to guess the aim of the experiment.

Show question

Question

How can researchers deal with confounding participant variables?


Show answer

Answer

Through matched pairs design, researchers can manipulate the participant variables. Extraneous participant variables like individual differences cannot be eliminated but can be reduced, improving internal validity.

Show question

Question

How are participants allocated in the matched pairs design?

Show answer

Answer

In the matched pairs design, one participant goes to one condition, and the other goes to a different one. 

Show question

Question

How would participants be matched in pairs?

Show answer

Answer

Participants are paired up in matched pairs based on a specific trait or variables relevant to the study. For example, by gender, IQ, age, ethnicity, socioeconomic status.

Show question

Question

What are confounding variables?

Show answer

Answer

Confounding variables are uncontrolled variables that can influence the dependent and independent variables.

Show question

Question

What are the strengths of matched pairs designs?

Show answer

Answer

  • No order effects.
  • Reduced demand characteristics.
  • Better control of participant variables. 

Show question

Question

What are the weaknesses of matched pairs designs?

Show answer

Answer

  • Lower economic benefit as it requires more participants.
  • It needs extra data to match the participants in pairs. 
  • If one participant drops out, the data for the pair is lost. 
  • It is time-consuming to find matching pairs.

Show question

Question

In an independent group design...

Show answer

Answer

different participants are used in each experimental condition. 

Show question

Question

Experimental designs measure the effect that...

Show answer

Answer

the independent variable has on the dependent variable 

Show question

Question

Which variable is manipulated in an independent group design?


Show answer

Answer

The independent variable is manipulated. 

Show question

Question


What is the dependent variable?

Show answer

Answer

The dependent variable is the variable which depends on the changes made to the independent variable. It is the 'effect' factor. 

Show question

Question

​How does independent group design differ from repeated group design? 


Show answer

Answer

Repeated group design uses the same individuals on two or more occasions for each experimental condition. Whereas independent group design uses different individuals.

Show question

Question

In order to fairly test the hypothesis, the groups must contain...

Show answer

Answer

the same number of individuals. 

Show question

Question

A key advantage to independent group design is that there are no order effects. What are order effects?

Show answer

Answer

Order effects refers to the order of the conditions having an effect on the behaviour of the participants. This is usually considered negative (e.g. boredom effects) and can decrease the validity of the results. 

Show question

Question

Why is requiring more participants in an independent group design an advantage? 


Show answer

Answer

It is an advantage because it increases the external validity of the results, making them more representative. 

Show question

Question

Why can requiring more participants be a disadvantage?

Show answer

Answer

It can be a disadvantage because it may mean that carrying out the experiment is more costly (i.e. requires more equipment). 

Show question

Question

What are participant variables?


Show answer

Answer

Participant variables are differing characteristics specific to the individuals that could influence how the participants respond in an experiment.

Show question

Question

'Participant variables always effect the validity of the results' 

Show answer

Answer

True. 

Show question

Question

How can we counteract participant variables?

Show answer

Answer

By using random sampling. 

Show question

Question

What does random sampling mean?

Show answer

Answer

Random sampling means that each member of population has an equal chance of being selected through random list generators on computers or placing names in a container and drawing them out randomly. 

Show question

Question

Why is random sampling important for experimental design?

Show answer

Answer

It is important because it encourages unbiased sampling and therefore unbiased results. 

Show question

Question

What is a hypothesis?

Show answer

Answer

A hypothesis is a suggestion based on limited evidence and a starting point for further investigation. 

Show question

60%

of the users don't pass the Experimental Designs quiz! Will you pass the quiz?

Start Quiz

Discover the right content for your subjects

No need to cheat if you have everything you need to succeed! Packed into one app!

Study Plan

Be perfectly prepared on time with an individual plan.

Quizzes

Test your knowledge with gamified quizzes.

Flashcards

Create and find flashcards in record time.

Notes

Create beautiful notes faster than ever before.

Study Sets

Have all your study materials in one place.

Documents

Upload unlimited documents and save them online.

Study Analytics

Identify your study strength and weaknesses.

Weekly Goals

Set individual study goals and earn points reaching them.

Smart Reminders

Stop procrastinating with our study reminders.

Rewards

Earn points, unlock badges and level up while studying.

Magic Marker

Create flashcards in notes completely automatically.

Smart Formatting

Create the most beautiful study materials using our templates.

Just Signed up?

Yes
No, I'll do it now

Sign up to highlight and take notes. It’s 100% free.