RM- experimental designs

How you are structuring an experiment

Control group

The independent variable is absent so there is no manipulation in the condition to get a baseline reading.

Experimental group

Manipulation of the independent variable to see how it affects the dependent variable.

What are the 3 types of research designs

Independent group design, repeated measures design and matched pairs design

Independent group design

Recruit participants, divide them into 2 separate groups and each group will sit a condition, measure the dependent variable for each group.

Pros of independent group design

Easy to run- can be used in many scenarios

Less time needed than repeated measures

No problem with the order or practice effect

Cons of independent group design

Individual differences- random allocation can reduce

Large sample needed- expensive

Random allocation

Participants are randomly allocated to the different conditions which hopefully balances the groups

Repeated measures

All participants do all conditions

Pros of repeated measures

No risk of individual differences impacting the results of the study

Less participants needed

Cons of repeated measures

Can experience demand characteristics- more opportunities to guess the purpose of the study

Order effect- performance can be affected due to tiredness, boredom or practice

How to overcome cons of repeated measures

Counterbalancing

Counterbalancing

Advanced form of repeated measures- half of the participants perform condition A first while the other half perform condition B first. This equally SPREADS the order effect

Matched pairs design

Participants are matched by a specific characteristics, they then will sit seperate conditions- it is the gold standard out of three

Matched pairs- pre-test

Participants must be matched by a pre- test

Pros of matched pairs

No order effect

Reduced risk of individual differences

Cons of matched pairs

Lots of participants needed to begin with- time consuming and expensive

Difficult to ensure pairs are matched adequately

Can’t control all individual difference