The Use of Carpeting in Hospitals, While Having Aesthetic Value

Multiple Choice

The use of carpeting in hospitals, while having aesthetic value, raises an obvious question: Are carpeted floors sanitary? An experiment comparing airborne bacteria levels in carpeted rooms with that in uncarpeted rooms was performed in an effort to answer this question. Specifically, for each of eight carpeted rooms and eight uncarpeted rooms in a hospital, the number of bacteria per cubic foot of air was measured. The data are given below. Assume that room sizes are equal, and that the 16 rooms in this experiment were assigned randomly to the carpet and no-carpet groups. If W, the Wilcoxon rank sum test statistic, is the sum of the ranks assigned to the carpeted group, and if the two populations have the same continuous distribution, then the standard deviation of W is:

A) 2.32.
B) 8.51.
C) 9.52.
D) 90.67.