2. Experimental Designs

Question 1

Independent Groups

Definition and example

Answer 1

• involves using different people in each condition

- e.g. in a drug trial, group A takes the drug, group b takes the placebo. They are not mixed

Question 2

Independent groups

Strengths and weaknesses

Answer 2

• S - avoids practice and order effects, can be quick and easy to set up
• W - a lot of participants needed, there may be some participant variability

Question 3

Repeated groups

Definition and example

Answer 3

• involves using the same people in each condition

- e.g. in a group trial group a takes the placebo then group A take the drug

Question 4

Repeated groups

Strengths and weaknesses

Answer 4

• S - Participant variability is kept constant, fewer participants are required
• W - order and practice effects are present, demand characteristics may be a problem

Question 5

Matched pairs

Definition and example

Answer 5

• involves using different participants in each condition but participants are matched or paired with another who is similar in a number of variables
• e.g. in a drug trial, each participant is paired with someone who closely matches them, one takes the placebo and the other takes the drug

Question 6

Matched pairs

Strengths and weaknesses

Answer 6

• S - p’s variability is partially controlled, avoids practice and order effects
• W - will need a lot of participants, participants are never perfectly matched