To help develop a hiring program, a personnel manager wanted to compare how long business graduates and non-business graduates worker for the company before taking a job elsewhere. The manager selected a random sample of 25 business graduates and 25 non-business graduates who had been hired five years ago. The number of months each had worked was recorded. Is there a difference at the .95 confidence level?

Business: 60 11 18 19 5 25 60 7 8 17 37 4 8 28 27 11 60 25 5 13 22 11 17 9 4

Non-Business: 25 60 22 24 23 36 39 15 35 16 28 9 60 29 16 22 60 17 60 32

A drug company is testing the effectiveness for a new painkiller. Thirty people were selected and half were given the new drug while the other half were given aspirin. Each rated the effectiveness of the drug on a five point scale:

5 = extremely effective
4 = quite effective
3 = somewhat effective
2 = slightly effective
1 = not effective

Painkiller: 3 5 4 3 2 5 1 4 5 3 3 5 5 5 4

Aspirin: 4 1 3 2 4 1 3 4 2 2 2 4 3 4 5

At the .95 confidence level, is there a difference?

In each of two years, a survey company asked 100 people whether spending on advertising of alcoholic beverages should be allowed to be the same (3), decreased (2), or eliminated completely(1). The sum of the ranks for last year were 10691 and for this year were 9409. At the .90 confidence level, is there a difference?

A new food additive is reported to cause upset stomachs. Fifty women and fifty men were survey after eating food prepared with this additive. They rated stomach upset on a four-point scale: 4-extremely upset, 3-somewhat upset, 2-mildly upset, 1-not upset. The sum of ranks for women were 2810, and for men, 2240. At the .90 confidence level, is there a difference?