An industrial psychologist devises a 50-point questionnaire to measure a worker's attitude toward his job; the higher the score, the more favorably the worker views it. The industrial psychologist is concerned that attitude may be affected by the relationship of the day questioned to payday, with a worker responding more favorably if he has been recently paid. To evaluate the effect of payday, she draws a random sample of 16 workers and gives them all the same questionnaire the day before (with score y1) and the day after (with score y2) they are paid. The difference in each worker's two scores (yd= y1 - y2) is the variable analyzed.

a. Give the most logical null and alternative hypotheses.

b. Use the sample data sum y1= 512, sum y2 = 608, sum (yd - y(mean)d)^2= 1500 and a = 0.05 to give the critical value of the test statistic. Make the test of significance.

c. Is there a payday effect?