Experimental designs

What is independent group design

Different participants used in each condition of an experiment

Strength of independent group design

There’s no order effects presented

Participants less likely to guess aim of study (demand characteristics)

Limitation of independent group designs

No control over participant variables- abilities of participant in various conditions can cause changes in DV

You need more participants than other designs to gather same amount of info

Solution of no control over participant variables for independent group designs

Use random allocation as it ensures each participant has same chance of being in 1 condition of IV as another

What are repeated measures

Same participant takes part in all conditions of the experiment

Strengths of repeated measures

Eliminates participant variables

Fewer participants needed so less time consuming

Limitations of repeated measures

Order effects presented e.g. boredom may mean in 2nd condition, participant don’t do as well on task

Solution to boredom of participants in repeated measures

Counterbalancing- half of participants do conditions in 1 order and other half do it in opposite order

What are matched pairs

Pairs of participants are first matched on a variable that’s affecting the dependent variable. Then 1 member of each pair does 1 condition and the other does another

Strengths of using matched pairs

no order effects

Demand characteristics are less of a problem

Limitations of using matched pairs

Time consuming and expensive to match

Large number of participants needed which can be difficult to get

Difficult to know which variables are appropriate for participants to be matched