Lecture 6 - factorial ANOVA

Question 1

ANOVA can simultaneously compare two means. What else can it do?

Answer 1

It can also allows us to test more than one independent variable at a time and see how they interact with each other

Question 2

When would you use a factorial ANOVA?

Answer 2

When you have more than one independent variable

Want to know if the means are really different or if the differences can be explained by error variability

Want to know if your independent variables interact with each other

Question 3

Factorial ANOVAs increase what in our study?

Answer 3

Generality of results - more complex experiments reflect the real world

Question 4

What are the main effects in a factorial ANOVA?

Answer 4

The separate effects of each of the independent variables
The effects of each IV collapsed across (ignoring the levels of any other variables)
Effect of what you’re testing on its own, effect of task on its own
Shows if the effects of one variable change at different levels of another variable

Question 5

When do two IVs interact?

Answer 5

When the effects of one variable are different at the different levels of the other variable - levels of the IV affect performance differently at different levels of the task IV

Question 6

What is interpretation of main events affected by?

Answer 6

The presence of interaction

Question 7

If we have an interaction between our IVs and we plot the data on a graph, what will this show?

Answer 7

The lines on the graph will not be parallel

Question 8

What is disordinal interaction?

Answer 8

Disordinal (crossover) interaction is when each variable is having the opposite effect at different levels of the other variable. It is the strongest form of interaction and has very misleading main effects

Question 9

What is ordinal interaction?

Answer 9

If the task Type only affected one variable and had no affect on the other - can interpret main events with caution

Question 10

What is meant by no interaction?

Answer 10

Main effects but no interaction, parallel lines on the graph, main effects accurately reflect the results

Question 11

In a repeated measures design, what are all the factors?

Answer 11

Within subjects

Question 12

In a between subjects design, what are all the factors?

Answer 12

Between subjects

Question 13

What are the factors in a mixed design?

Answer 13

Some factors are within subjects and some factors are between subjects

Question 14

What are the advantages of a factorial design?

Answer 14

Economic- more info less cost
Eliminating confounds - instead of controlling extraneous variables they can be included as extra IVs - more realistic
Factorials allow you to study interactations

Question 15

What does a factorial ANOVA give separate tests for?

Answer 15

Main effects

Interactions

Question 16

In which ANOVA test you find within treatment variance?

Answer 16

Between subjects ANOVA

Question 17

In which ANOVA would you find residual error variance?

Answer 17

Repeated measures ANOVA

Question 18

What would we need to add for a factorial design on ANOVA?

Answer 18

Between treatments variance is further sub divided into components for the main effects of each factor and for their interaction - the estimation for each component follows same logic as before

Question 19

How do you work out the interaction variability?

Answer 19

Work out goal between group variability (deviation of each treatment mean from overall mean)
Work out main effect variability (look at variability due to each IV separately) - deviation of the means for each condition of each IV from the overall mean
Total between group variability - main effect variability = interaction variability

Question 20

What does ANOVA mean?

Answer 20

Analysis of Variance

Question 21

How can total variability be divided?

Answer 21

F = (main variance + interaction variance) divide by error (individual differences + residual error)

Question 22

What does k mean in an SPSS table?

Answer 22

Number of levels of variance

Question 23

How would you find the F value for variable A?

Answer 23

MSbtw/MsError

Question 24

How would you get MSbtw for variable A?

Answer 24

SS/df