1. The Wilcoxon rank sum test is suitable when

Select one:

a.

The dependent variable is qualitative on the nominal scale.

b.

Thedependent variable is qualitative on the ordinal scale.

c.

The dependent variableis quantitative and it is normally distributed.

d.

None of the above.

2. Suppose that a survey on custormer satisfaction allows the following responses:

• Not satisfied
• Somewhat satisfied
• Extremely satisfied

Which of the following is not a valid numerical assignment for the ordinal responses variable?

a.

• 1: Not satisfied
• 3: Somewhat satisfied
• 2: Extremely satisfied

b.

• 101: Not satisfied
• 102: Somewhat satisfied
• 104: Extremely satisfied

c.

• 1: Not satisfied
• 3: Somewhat satisfied
• 5: Extremely satisfied

3. Suppose the U.S. Consumer Product Safety Commission (CPSC) wants to test the hypothesis that New York City electrical contractors are more likely to install unsafe electrical outlets in urban homes than in suburban homes. A pair of homes, one urban and one suburban, and both serviced by the same electrical contractor, is chosen for each of 10 randomly selected electrical contractors. A CPSC inspector assigns each of the 20 homes a safety rating between 1 and 10, with higher numbers implying safer electrical conditions. The results are shown below:

Contractor	Urban Home	Suburban Home
1	7	9
2	4	5
3	8	8
4	9	8
5	3	6
6	6	10
7	8	9

An analyst conducted the following analysis:

Step 1: let the safety score of urban home be population A and thesafety score of suburban score by population B.

H0:The two populations location are the same HA:The location of pop A is to the left of the location of pop B

Step 2: set level of significance at 5%, i.e.= 0.05.

Step 3: the test statistic is Wilcoxon Rank Sum of population A sincenA =nB. Step 4: from Excel, the rank sum of sample A isWA= 42.5.

Step 5: from the Wilcoxon Rank critical value table, we obtainTL= 39andTU= 66fornA= 7andnB= 7. SinceT= 42.5 >TL, we do not reject the null.

You are asked toevaluate this analyst's work. Which of the following statements do you agree with?

a. The analyst's work is correct.

b. The analyst has used the wrong critical value. The correct critical values are TL=37 and TU=68.

c. The analyst has wrongly stated the alternatively hypothesis. The correct alternative hypothesis is that " the pop A is located to the right of pop B".

d. The analyst has used the wrong test statistic. The correct test statistic is the rank sum of sample B.

e. The analyst has used the wrong test. The Wilcoxon rank sum test is used for independent samples but the samples in this example is paired.