Experimental Designs

Question 1

Independent measures design

Answer 1

• 2 sepearate groups of pts experience 2 different conditions of the experiment.
• if there are 2 IV then all pts only experience one level of the IV

Compare the results

Question 2

Repeated measures design

Answer 2

• all pts experience both conditions of the experiment

Question 3

Matched pairs

Answer 3

• pts paired together on a variable or variables relevant to the experiment.
• one pts from each pair would be allocated to different condition of the experiment
• to control the confounding variable of pts variables

Question 4

Evaluate independent measures design

Answer 4

Confounding variables:
- pts don’t have the same pts variables
- if researcher finds a mean difference between a group on the DV -> could be due to the pts variables rather than the IV
- researchers use random allocation to account for this : evenly distribute pts characteristics across the conditions

Less economical:
- twice as many pts needed to produce equivalent data to the data collected in repeated measures.
… increases time and money spent on more pts
- order effects are not an issue

Question 5

Evaluate repeated measures

Answer 5

Issue of order effects:
- the order in which the pts do each condition is significant… so we use counterbalancing {control order effects, half the pts do condition A then B, the others do B then A}
- demand characteristics… pts will work out the aim of the study when they experience all the conditions of the exp.

Pts variables are controlled:
- so few pts needed {less time spent recruiting them}

Question 6

Evaluate matched pairs

Answer 6

• Less chance of order effects and demand characteristics; pts take part in only one condition
• pts can’t be matched exactly; differences can still effect the DV
• matching pairs can be time consuming and expensive