Experimental Research Designs

Repeated groups

The same participants are used in both conditions

Strengths of repeated groups

• Individual differences are kept constant as it is the same participants in each conditions

• Fewer participants are needed (15 minimum)

Weaknesses of repeated groups

• Order effects may occur as participants might get bored in the second condition and not try as hard or may have received practice from the first attempt - counterbalancing needed

• Demand characteristics

• Different tests may be needed for each condition, but they will need to be of equal difficulty otherwise it will become a confounding variable but it is unlikely the tests will be of equal difficulty

Counterbalancing

Used to overcome order of effects

Group 1 do condition 1 first then condition 2 second, while group 2 does condition 2 first then condition 1 second.

Both will still suffer from order of effects in the second attempt but the 2 groups will cancel each other out

Independent group design

Different participants used in each condition and are randomly allocated to groups

Strengths of independent groups

• Order effects don’t occur as each participant is only in one condition- more likely that the results are due to the IV rather than practice or boredom

• Demand characteristics are less of a problem because they only experience one part of the IV, making it harder to guess the aim

• Same test can be used in each condition

Weaknesses of independent groups

• Individual differences are not kept constant as it’s different participants in each condition

• More participants are needed

Matched pair design

Similar but different participants are used in each condition. Effort is made to match participants on important characteristics that may affect performance in the study

Strengths of matched pair design

• Individual differences are kept constant as the participants have been matched on important characteristics, therefore DV should be due to the manipulation of IV

• Order effects don’t occur as each participant is only in one condition so it is more likely the results are due to the IV

• Demand characteristics are less of a problem because participants only do one condition and only experience one IV so it is less likely they guess the aim

• Same test can be used in each condition

Weaknesses of matched pairs

• Individual differences can never be fully matched

• Matching participants is time consuming and difficult in reality