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 SAD patients 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 Time of Day

Low Morning 5 6 4 7 5 6 Night 5 8 6 6 4 3

Medium Morning 4 6 4 7 9 8 Night 6 8 7 5 8 8

High Morning 7 8 6 9 5 8 Night 9 7 6 8 7 6

(a) Complete theF-table and make a decision to retain or reject the null hypothesis for each hypothesis test. (Round your answers to two decimal places. Assume experiment wise alpha equal to 0.05.)

Time of day SS ________ df ________ MS _______ F _________

Intensity SS ________ df ________ MS _______ F __________

Time of day Intensity SS __________ df ___ MS______ F __________

Error SS _____ df ____ MS ________

Total SS ____ df ____

State the decision for the main effect of the time of day.

Retain the null hypothesis.

Reject the null hypothesis.

State the decision for the main effect of intensity.

Retain the null hypothesis.

Reject the null hypothesis.

State the decision for the interaction effect.

Retain the null hypothesis.

Reject the null hypothesis.

(b) Compute Tukey's HSD to analyze the significant main effect.

The critical value______ is for each pairwise comparison.

Summarize the results for this test using thinking skills.