Lecture 4- Experimental Design 3

Question 1

What does multiple independent variables allow for?

Answer 1

Allows a determination of not only the effect of each IV on the DV but how they interact as well,,as the relationship between one IV and
the DV may change as the levels of the other IV(s) change

Question 2

What is factorial design?

Answer 2

Factorial design is the experiment design used when there are multiple independent variables. It is called this because each IV is called a factor.

When each level of one factor is combined with every level of the other factor (all combinations covered) then the design is fully crossed. This is ideal.

Question 3

What is a 2x2 factorial design? What number of possible conditions results?

Answer 3

Occurs when each IV has 2 levels

2x2= 4 possible conditions

Question 4

How many possible conditions results from a 3x3 factorial study design?

Answer 4

9

Question 5

Describe how a between subjects study is carried out in a factorial design…

Answer 5

• All IVs are between-subjects IVs
• Each participant is randomly assigned to one of the possible conditions created by combining the levels of the IVs (only experience one condition)

Question 6

Describe how a within subjects study is carried out in a factorial design…

Answer 6

• All IVs are within-subjects IVs
• Each participant receives each of the possible conditions created by combining the levels of the IVs (they experience all possible conditions)

Question 7

Describe how a mixed subjects study is carried out in a factorial design…

Answer 7

• One IV is within-subjects, one IV is between-subjects

- Each participant receives each level of the within-subjects IV and one level of the between subjects IV

Question 8

What two effects are seen with factorial designs?

Answer 8

• Main effects

- Interaction effects

Question 9

What are main effects?

Answer 9

• The effects of one IV on the DV, ignoring the other IV(s) in the study
• There is a main effect for each IV

Question 10

How do you calculate the main effect of one IV on the DV without taking into account the other factor?

Answer 10

We average out the two results we have for the IV we want at both levels and then compare these.

When we average we are taking out the effect of the other variable

Question 11

What are interaction effects?

Answer 11

• The effects of one IV on the DV, taking into account the other IV(s) in the study
• There is an interaction for every combination of IVs

To do this we Look at the relationship between one factor and the DV and see how it changes as the levels of the other factor(s) change

Question 12

How do you calculate interaction effects?

Answer 12

Minus across the table for the factor you want to study and then see the difference

Question 13

What do you interpret first- main effects or interactions?

Answer 13

Interactions

Question 14

What can a graph tell us about whether there is an interaction between variables/ IVs?

Answer 14

-If the lines diverge or intersect, then there is an interaction
-If the lines are parallel, then there is no interaction, and main effects may
or may not be present

Question 15

What are the three sources of variability in a 2-factor experiment?

Answer 15

• 2 main effects (1 for each IV)

- 1 interaction effect

Question 16

Are interaction and main effects dependent on each other?

Answer 16

• Interaction and main effects are not dependent on each other in any way
  i. e. can have no main effects or interaction, any one, any two or all three