Question

A) Which is not true concerning the one sample sign test?

a. Data is collected from a random sample

b. Ranks of the difference must be calculated

c. Test is based on the binomial distribution

B) Which is not true statement about the Wilcoxon signed-rank test?

a. Data is collected from a random sample

b. Ranks of the difference must be calculated

c. If sample exceeds 20, then the test cannot be done

C) Which is not true statement concerning the Mann Whitney U test?

a. Data is collected from a random sample

b. Ranks of the difference must be calculated

c. The two samples are equal in size

Answer 1

A) Ranks of the difference must be calculated is incorrect statement. We just count the number of positive and negative signs. Ranking the data is not required. Other two statements are correct since data collected is a random sample and we find the p value using binomial distribution. ANSWER : option B

B ) if sample exceeds 20 then test cannot be done is incorrect statement. If sample is large then we assume that ranks follow normal distribution . We find mean and standard deviation of ranks and test using test statistic z . Other two statements are correct since data is random sample and also ranking the differences ( if not zero) is required. If difference is zero we ignore it and reduce the sample size.

ANSWER: option C

C ) Ranks of difference must be calculated is incorrect statement. We have to combine the sample and rank the data while keeping track of which sample point comes from which sample . So there is need to find the difference between samples points. Other two statements are correct . Sample is random sample and two samples can be equal or can vary in size. ANSWER : option B