26.

For each of the following, state whetherF= 0

for a main effect, the AB interaction, or both.

(a) Cell means are equal.

F= 0 for a main effect.

F= 0 for the AB interaction.

F= 0 for a main effect and the AB interaction.

(b) Row totals are equal.

F= 0 for a main effect.

F= 0 for the AB interaction.

F= 0 for a main effect and the AB interaction.

(c) Column totals are equal.

F= 0 for a main effect.

F= 0 for the AB interaction.

F= 0 for a main effect and the AB interaction.

27.

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 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.)

Source of

Variation SS df MS F

Time of day

Intensity

Time of day

Intensity

Error

Total

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

_________________________________