Lecture 6: Experimental Designs

Question 1

What are experimental designs?

Answer 1

aim to determine causal influences

Question 2

What do strong experimental designs do?

Answer 2

rule out alternative explanations (confounding variables) therefore having high external validity

Question 3

What are confounding variables?

Answer 3

variables that are connected to the IV that could actually explain the change in DV

Question 4

What are the different kinds of experimental designs?

Answer 4

• between-subjects designs
• within-subjects designs

Question 5

What is common across experimental designs?

Answer 5

the goal to determine causal influence of the IV and to rule out the influence of confounds

Question 6

What are between-subjects designs?

Answer 6

different participants are assigned to each level or condition of the IV

Question 7

What are within-subjects designs?

Answer 7

the same group of participants are assigned to each level or condition of the IV

Question 8

How much the IV be operationalized in experimental designs?

Answer 8

to have at least 2 levels/conditions

Question 9

What is a disadvantage of between-subjects designs?

Answer 9

selection/individual differences

Question 10

What are selection/individual differences?

Answer 10

the notion of pre-existing differences between the two groups experiencing two levels of IV

Question 11

What are ways to reduce selection/individual differences?

Answer 11

• random assignment
• pretest-posttest design
• matched pairs design

Question 12

What is a disadvantage of within-subjects designs?

Answer 12

the internal validity due to order effects

Question 13

What are order effects and what are the different types?

Answer 13

when the order of conditions has an influence on the DV
- practice effects
- fatigue effects
- contrast effects

Question 14

What are practice effects?

Answer 14

participants perform better over time because of repeated experience with study tasks

Question 15

What are fatigue effects?

Answer 15

participants perform poorer over time because they are tired or bored/inattentive

Question 16

What are contrast effects?

Answer 16

participant responses following a later condition are impacted by experience in earlier condition

Question 17

How are order effects reduced?

Answer 17

by counterbalancing IV conditions with different people experiencing different orders

Question 18

What are advantages of between-subjects designs?

Answer 18

• random assignment can reduce issue of selection differences
• group differences support effect of IV manipulation

Question 19

What are disadvantages of between-subjects designs?

Answer 19

• selection differences could confound results
• need larger sample (n > 50 per IV condition)

Question 19

What are advantages of within-subjects designs?

Answer 19

• fewer participants needed (n > 50 total)
• individual differences are not an issue
• can detect very small differences

Question 20

What are disadvantages of within-subjects designs?

Answer 20

• order effects
• participants may guess your hypothesis and change behaviour