1. A health psychologist investigates the number of viral infections people contract as a function of the amount of psychological stress they experience during a one-year period. She wants to see if there are significant differences (at the significance level of 0.05) in the mean number of viral infections depending on the amount of stress. She obtained the following data (N=20):

_____________________________________________________

Negligible Minimal Moderate Severe

Stress Stress Stress Stress

_____________________________________________________

2 4 6 5

1 3 5 7

4 2 7 8

1 3 5 4

2 2 6 8

_____________________________________________________

Please answer the following questions:

(a) What are the null and alternative hypotheses?

(b) What assumptions should be made? Provide 4 assumptions.

1)

2)

3)

4)

(c) What are the critical values? (Specify df_between and df_within first). Then, using the critical value, specify the decision rules.

(d) Computation: Provide the ANOVA table (show the process of computation)

Source SS df MS F

Between

Within N/A

Total

(e) What are your decisions? Provide interpretation of your results.