experimental design

independent groups

participants are divided into two separate groups: one group do condition A, one group do condition B

repeated measures

there is only one group of participants: they take part in both conditions of the experiment

matched pairs

participants are tested before taking part and are matched for qualities into pairs: they will be identified Aa, Bb, Cc, Dd

order effects

a confounding variable arising from the order which participants take place in the different conditions

counter balancing

alternation of the order of conditions to control order effects in repeated measure design

independent groups strengths

- no order effects: different P's in each condition

- less chance of demand characteristics: P's less likely to guess the aim of the study

independent groups weaknesses

- more P's needed: different P's in each condition, need a larger sample

- individual differences: different P's in each condition, so comparing results of each condition not accurate

repeated measures strengths

- less P's needed: same people in each condition

- controls for individual differences: same people in each condition

repeated measures weaknesses

- more materials needed: the same test can't be used for the P's

- more chance of demand characteristics: P's are more likely to guess the aim of the study

matched pairs strengths

- no order effects: different P's in each condition

- less chance of demand characteristics: P's less likely to guess aim of study

matched pairs weaknesses

- matching is difficult: impossible to match all participant variable

- time consuming: lengthy process to match P's before the experiment