1. Analysis of Variance: ANOVA

2. Group 1: control group/ no ind. Var. Group 2: low level of the ind. Var. Group 3: high level of the ind var.

3. If you evaluated the differences using a t test: group 1 vs. group 2 group 2 vs. group 3 group 1 vs. group 3

4. What is the probability of a type one error somewhere in this analysis?

5. Type One error: rejecting the null when there really isn’t any effect of the independent variable. Reject the null

6. The probability of a type one error in a single comparison is whatever the probability of a random event is. P <.05 or 5% of the time

7. Probability over three comparisons: type one error in comparison one or comparison two or comparison three

8. Probability of type one error:.05 +.05 +.05 =.15 or 15% of the time

9. This inflation of the type one error rate is known as: Experimentwise error rate

10. To hold down the experimentwise error rate we perform an analysis of variance (ANOVA) instead of multiple t tests.

11. variance between groups F = --------------------------------------- variance within groups

12. Var. between : how much each group mean differs from all other group means.

13. Var. within: how much individuals within the groups vary from each other.

14. What causes variability between : treatment + random events independent variable confounding factors

15. What causes variability within : Random events (individual differences)

16. treatment + random events F = ------------------------------------------------ random events

17. When the only thing that has caused the groups to differ is random events, F should be a value very close to 1

18. variance Sum of squares (SS) Degrees of freedom (df)

19. In ANOVA: Variance is known as the mean square (MS)

20. Sum of Squares Variance = ------------------------------- degrees of freedom

26. Where K represents the number of groups