1. Chapter 14 Homework: problem 1
Post Hoc Tests
Chapter 14
Homework: problem 1

2. Interpreting ANOVA ANOVA: testing omnibus null hypothesis
H0 : m1 = m2 = m3 = … = mk
Accept H0
all possible pairwise and complex H0 are true
Reject H0
at least one is false
do not know which one(s) ~

3. Post Hoc Tests Post hoc: after the fact only after rejecting ANOVA H0
Hypothesis tests
Determine which means differ from each other
or combination of means
complex hypotheses
several different types of post hoc tests ~

4. Post Hoc Tests Cannot use t test
must set a before collecting and examining data
e.g., flip a coin
P(heads), before you flip?
P(heads) if you flip and peek?
ANOVA then t test is like peeking
P(Type 1 error) no longer a = .05 ~

5. Post Hoc Test: Tukey’s HSD
HSD: honestly significant difference
Use to test pairwise H0
only after significant ANOVA
Test statistic is Q
studentized range statistic (A.5, p480)

6. Post Hoc Test: Tukey’s HSD
MSW is mean squared within groups
s2pooled
unequal n use MSW from ANOVA ~

7. Tukey’s HSD: QCV Table A.5, p. 480 (a = .05) p. 481 (a = .01)
need 2 pieces of information
1st column: dfW
(nG - k)
1st row: k = # groups
NOT dfB = k - 1
Find QCV same as others ~