Experimental Design

What is Experimental Design?

How participants are allocated to different groups in an experiment.

What are the 3 types of experimental design?

• Repeated measure design

• Independant group design

• Match pair design.

What is Repeated Measure design?

• Same participants take part in each condition of the IV.

• Usually tests people twice.

• Eg: Testing students concentration levels before and after lunch.

What are the limitations of the Repeated measure design?

• Order effect: Participants get fatigued or bored doing things repeatedly.

• Participants might try to find out about the investigation.

• Participants may imprive due to practise.

What are strengths of Repeated Measure design?

• Participant variables are controlled

• Extra participants aren’t needed

What is Independent Groups Design?

• Participants are used in each condition of IV.

• In each condition there are 2 groups.

• The performance of both groups, one is experimental condition and the one is control condition.

• Usually in natural conditions, out of a lab.

What are strengths of Independant Groups design?

• Removes order effect

• No participant is used in more than one conditions.

• Less consuming

What are limitations of Independent Groups design?

• Participants vary, individual effects results between conditions, no manipulating IV.

• More participants are needed.

What is Match-Pair Design?

• When participants are matched on key variables for shared characteristics relevant to the topic of the study.

• One member of each pair is placed into the control group while the other is placed into the experimental group.

What is an example of Match-pair design?

• A researcher wants to see how much new diets affect weight loss compared to standard diets.

• Two treatment conditions are there so they can be match pair design.

• In total there’s 100 subjects, then grouped into 50 pairs based on age, gender or other factors.

• Within the pair one is in the new diet and one is on the old.

• After 30 days, researcher measures weight loss for both and compares.

What are limitations of Match-pair design?

• Time consuming

• More participants are needed

What are strengths of Match-pair design?

• More accuracy as there is less difference between participants.

• No order effect

• More realistic