Question

The mean and the standard deviation of W for the nonparametric Wilcoxon rank sum test depend:
	on the number of items that are being ranked but not on the values themselves. entirely upon the characteristics of the two samples. entirely upon the characteristics of the two populations. on the number of items that are being ranked as well as the values themselves.

13.	The Wilcoxon signed rank test is used for small samples when Normality cannot be established or is known not to hold for:
	All of the above paired data. two independent samples with unequal variances. more than two groups.
A study was conducted to assess the effects of caffeine on concentration. Fifteen subjects were recruited into the study and randomly divided into three groups of equal sample size. Group 1 was given an 8-ounce cup of coffee, group 2 an 8-ounce cup of black tea, and group 3 was given an 8-ounce cup of decaffeinated coffee. Each subject was then shown a set of 20 numbers for 1 minute. The subjects were then asked to enter five of the numbers they had been shown and the time it took was recorded. A statistician told the investigators they should use a nonparametric test since their data was unlikely to be Normally distributed and their sample was small. The researchers consulted the literature on nonparametric tests and found several. An appropriate test here be a:
	Wilcoxon rank sum test. Kruskal-Wallis test. Wilcoxon signed rank test. Mann-Whitney test.

Answer 1

Solution:

The mean and the standard deviation of W for the nonparametric Wilcoxon rank-sum test depend

Answer: On the number of items that are being ranked but not on the values themselves.

The mean and standard deviation of Wilcoxon-rank-sum test depends on the number of items used

The Wilcoxon signed-rank test is used for small samples when Normality cannot be established or is known not to hold for:

Answer: Paired data

The Wilcoxon signed-rank test is used when the data is dependent

A study was conducted to assess the effects of caffeine on concentration. Fifteen subjects were recruited into the study and randomly divided into three groups of equal sample size. Group 1 was given an 8-ounce cup of coffee, group 2 an 8-ounce cup of black tea, and group 3 was given an 8-ounce cup of decaffeinated coffee. Each subject was then shown a set of 20 numbers for 1 minute. The subjects were then asked to enter five of the numbers they had been shown and the time it took was recorded. A statistician told the investigators they should use a nonparametric test since their data was unlikely to be Normally distributed and their sample was small. The researchers consulted the literature on nonparametric tests and found several. An appropriate test here be a:

Answer: Kruskal-Wallis test

Because we have to compare more than two groups