1. Analysis of Variance (ANOVA)

2. ANOVA data Grand Mean = 4.375 Control Placebo Drug 5 6 2 8 3 4 1 7 101 7 10
Mean = 6.5
Mean = 4.5
Mean = 2.125
Grand Mean = 4.375

3. Independent t-test

4. Variance

5. ANOVA data Grand Mean = 4.375 Control Placebo Drug 5 6 2 8 3 4 1 7 101 7 10
Mean = 6.5
Mean = 4.5
Mean = 2.125
Grand Mean = 4.375

6. Variance
total variance = within groups variance + between groups variance

7. May Affect Number of Headaches
genetics
stress
diet
gender
sleep …
new drug
Error
--- IV

8. ANOVA data IV (drug) error Control Placebo Drug 5 6 2 8 3 4 1 7 101 7 10
Mean = 6.5
Mean = 4.5
Mean = 2.125
IV (drug) error

9. Between-group var = IV + error
Within-group var = error
F = between var / within var =
(IV+error) / error
If IV has no effect, F = error/error = 1
Is F significantly greater than 1?