Page 213 - Statistics II for Dummies

Chapter 11: Finding Your Way through Two-Way ANOVA 197

Factor A is significant but not Factor B
Figure 11-1b shows that blood pressure changes increase across dosage
levels for people taking the drug once or twice a day. However, the two lines
are so close together that it makes no difference whether you take the drug
once or twice a day. So Factor A (dosage) is significant, and Factor B (times
per day) isn’t. Parallel lines indicate no interaction effect.

Change in BP 2 times/day

1 time/day

a 10mg 20mg 30mg
(dosage)

Change in BP 2 times/day
1 time/day

b 10mg 20mg 30mg
(dosage)

Change in BP 2 times/day

1 time/day

c 10mg 20mg 30mg
(dosage)

Change in BP 2 times/day

1 time/day

d 10mg 20mg 30mg
(dosage)
Figure 11-1:
Five exam- 2 times/day
ples of the
results from
a two-way Change in BP
ANOVA with 1 time/day
interaction.
e 10mg 20mg 30mg

17_466469-ch11.indd 197 7/24/09 9:44:17 AM