Does the time of day during which one works affect job satisfaction? A study in the Jo~~rnul of Occupational Psychology (Sept. 1991) examined differences in job satisfaction between day-shift and night-shift nurses. Nurses' satisfaction with thcir hours of work, free time away from work, and breaks during work were measured. The following table shows the mean scores for each measure of job satisfaction

(higher scorcs indicate greater satisfaction), along with thc observed significance level comparing the means for the day-shift and night-shift samples:

.................................................................................................................

Mean Satisfaction ......................................................................

Day Shift Night Shift p-Value .................................................................................................................

Satisfaction with:

Hours of work 3.91 3.56 313 Free time 2.55 1.72 ,047 Breaks 2.53 3.75 ,0073

a. Specify the null and alternative hypotheses if we wish to test whether a difference in job satisfaction exists between day-shift and night-shift nurses on each of the three measures. Define any symbols you use.

b. Interpret thep-value for each of the tests. (Each of the p-values in the table is two-tailed.)

C. Assume that each of the tests is based on small samples of nurses from each group. What assumptions are necessary for the tests to be valid?