Experimental Design: The different ways in which participants can be organised in relation to the experimental conditions.

Independent Group Design: Participants are allocated to different groups where each group represents one experimental condition.

Independent Groups Evaluation: The differences in dependent variable can have more to do with participant variables than the effects of the IV which may reduce the validity of the findings. researchers can use random allocation to overcome this. Independent groups are also less economical as they require twice as many participants as matched pairs. However there are no order effects unlike in repeated measures.

Repeated Measures: All participants take part in all conditions of the experiment.

Repeated Measures Evaluations: The order of the tasks done could be significant. Order effects could also occur as repeating two tasks could create boredom or fatigue which could effect performance. Participants could also work out the aim of the study. However, participant variables are controlled (higher validity) and less participants are needed.

Matched Pairs Design: Pairs of participants are first matched on some variables that may affect the dependent variable. Then one member of the pair is assigned to Condition A and the other to Condition B. This is in an attempt to control for the confounding variable of participant variables.

Matched Pairs Evaluation: Order effects and demand characteristics are less of a problem however participants can never be matched directly and matching may be time-consuming and expensive.

Random Allocation: An attempt to control for participant variables in an independent groups design which ensures that each participant has the same chance of being in one condition as any other.

Counterbalancing: An attempt to control for the effects of order in a repeated measures design: half the participants experience the conditions in one order, and the other half in the opposite door. (ABBA)