A researcher conducted a study on the effects of stress on migraines. The researcher computed the number of migraines individuals reported during a six-month time frame as a function of the amount of stress they reported during that same time period. There were three stress levels: low, mild, and severe. The sums of squares appear in the following ANOVA table. The means for each condition and the number of participants per condition are also provided.
|
Source
|
df
|
SS
|
MS
|
F
|
|
Between groups
|
|
22.167
|
|
|
|
Within groups
|
|
14.750
|
|
---------
|
|
Total
|
|
36.917
|
---------
|
----------
|
|
Stress Level
|
Mean
|
N
|
|
Low
|
3
|
4
|
|
Mild
|
4
|
4
|
|
Severe
|
6
|
4
|
a) Complete the ANOVA summary table.
b) Is Fobt significant at a = .05?
c) Perform post hoc comparisons, if necessary.
d) What conclusions can be drawn from the F-ratio and the post hoc comparisons?
e) What is the effect size, and what does it mean?