Two-Way ANOVA

33 Pages·2010·0.45 MB·English

Two-Way ANOVA
Chapter 11
Golf anyone?
A sports psychologist is interest in comparing the
effects of two instructional methods on golf performance.
100 novice golfers (50 boys and 50 girls)
IV: Method Type Method I Method II
DV: Golf proficiency 65 55
Gender Effects
100 novice golfers
IV: Sex 50 Boys 50 Girls
DV: Golf proficiency 60 60
Can we ignore sex in our interpretation of the Method Type effect?
Factorial Design
Method
I II
Girls 55 65 60
Boys 75 45 60
65 55
The instructional method interacts with sex
80
70
60
I
50
II
40
30
20
Girls Boys
“Interaction” Defined
An interaction is present when the effects of one IV
depend upon a second IV
“Interaction effect”: The effect of each IV across the levels of the other IV
When there is an Ia, the effect of one IV depends on the level of the other IV
80
70
60
I
50
II
40
30
20
Girls Boys
Factorial designs:
Designs with more than 1 IV
Levels of processing lab

IV: conditions (3 levels: letter, rhyme, sentence)

IV: correct response (2 levels: yes, no)

DV: accuracy

Therapy and disorder

IV: therapy (3 levels: psychoanalysis, behavioral, none)

IV: disorder (3 levels: depression, anxiety, schizophrenia)

Complete factorial design

All levels of each IV are paired w/ all levels of other IV

Incomplete factorial design

Not all levels of each IV are paired

Factorial notation

# levels of IV x # levels of IV

1 2
E.g.: 2 x 2 design vs. 3 x 2 design vs. 3 x 2 x 4 design etc.!!

Outcomes from Factorial ANOVA
Experiment has two factors, A and B
Each has 2 levels (so, 2 x 2 ANOVA)
B1 B2
A1 30 30 A1 Mean=30
10 point difference
A2 40 40 A2 Mean=40
B1 Mean B2 Mean
=70 =35 =35 =70
Main Effect of A
No Difference
Data show main effect of A
No main effect of B
No Main Effect of B
No interaction
Outcomes from Factorial ANOVA
Experiment has two factors, A and B
2 x 2 ANOVA
B1 B2
A1 30 40 A1 Mean=35
10 point difference
A2 40 50 A2 Mean=45
B1 Mean B2 Mean
=80 =35 =45 =80
Main Effect of A
10 point difference
Data show main effect of A
Data show main effect of B
Main Effect of B
No interaction
Outcomes from Factorial ANOVA
Experiment has two factors, A and B
2 x 2 ANOVA
B1 B2
A1 10 20 A1 Mean=15
0 point difference
A2 20 10 A2 Mean=15
40 B1 Mean B2 Mean 20
=15 =15
No Main Effect of A
0 point Difference
No main effect of A
No main effect of B
No Main Effect of B Data show an interaction
Line graphs:
main effects and interaction
50 60
50
40
40
30
30
20
20
10 10
1 2 1 2
25
20
15
10
5
0
1 2