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 dfbetween and dfwithin first)
(d) Specify the decision rules?
(e) Computation: Provide the ANOVA table
Source SS df MS F
Between
Within N/A
Total
(f) What are your decisions? Provide interpretation of your results.