Chapter 12: Experiments with multiple independent variables

Question 1

What is an interaction effect and what are the three options for interaction?

Answer 1

There is an interaction effect if one variable depends on the level of another variable

Three options:
- No interaction (parallel lines)
- Crossover interaction (crossing lines)
- Spreading interaction (spreading lines)

Question 2

What is a factorial design?

Answer 2

A design in which there are two or more independent variables

Question 3

How many conditions are in a 3x2 design?

Answer 3

6 conditions

Question 4

What is the difference between a manipulated variable and a participant variable?

Answer 4

A manipulated variable is an independent variable that the researcher manipulates

A participant variable is sort of an independent variable, but it can’t be manipulated by the researcher (e.g. age)

Question 5

What is a moderator?

Answer 5

Independent variable that changes relationship between two other variables. Presence of a moderator always indicates an interaction

Question 6

What are two reasons to use a factorial design?

Answer 6

• Testing generalizability of a causal variable
• Testing theories that make statements about interaction of variables

Question 7

What is a main effect and how do you calculate it?

Answer 7

The overall effect of one independent variable on the dependent variable.

You calculate it by comparing marginal means of the independent variable

Question 8

What are marginal means?

Answer 8

Arithmetic means for each level of the independent variable

Question 9

What are more important; interactions or main effects?

Answer 9

Interactions

Question 10

What is an independent-groups factorial design (between-subjects)?

Answer 10

Groups undergo different conditions.
If 2x2 design –> 4 conditions needed

Question 11

What is a within-groups factorial design (repeated-measures)?

Answer 11

Groups undergo all conditions and therefore fewer participants are needed

Question 12

What is a mixed factorial design?

Answer 12

One independent variable can be manipulated as independent-groups, but the other is manipulated as within-groups.

If 2x2 design –> need 2 groups

Question 13

What is a three-way design?

Answer 13

A design with 3 independent variables, such as 2x2x2 = 8 conditions

There are:
- 3 main effects
- 3 seperate two-way interactions
- 1 three-way interaction

Question 14

How do you recognize a threeway interaction from a graph?

Answer 14

If the two graphs both show different patterns, there is a threeway interaction

Question 15

How do you recognize factorial designs in the text?

Answer 15

• It depends..
• Only when..
• Especially when..