Seasonal affective disorder (SAD) is a type of depression during seasons with less daylight (e.g., winter months). One therapy for SAD is phototherapy, which is increased exposure to light used to improve mood. A researcher tests this therapy by exposing a sample of patients with SAD to different intensities of light (low, medium, high) in a light box, either in the morning or at night (these are the times thought to be most effective for light therapy). All participants rated their mood following this therapy on a scale from 1 (poor mood) to 9 (improved mood). The hypothetical results are given in the following table.
Light Intensity | ||||
---|---|---|---|---|
Low | Medium | High | ||
Time
of Day |
Morning | 5 | 5 | 7 |
6 | 6 | 8 | ||
3 | 4 | 6 | ||
7 | 7 | 9 | ||
5 | 9 | 5 | ||
6 | 8 | 8 | ||
Night | 5 | 6 | 9 | |
8 | 8 | 7 | ||
6 | 7 | 6 | ||
7 | 5 | 8 | ||
4 | 9 | 7 | ||
3 | 8 | 6 |
(a) Complete the F-table and make a decision to retain or reject the null hypothesis for each hypothesis test. (Round your answers to two decimal places. Assume experimentwise alpha equal to 0.05.)
Source of Variation |
SS | df | MS | F |
---|---|---|---|---|
Time of day | ||||
Intensity | ||||
Time
of day × Intensity |
||||
Error | ||||
Total |
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