Question

A certain marathon has had a wheelchair division since 1977. An interested fan wondered who is​ faster: the​ men's marathon winner or the​ women's wheelchair marathon​ winner, on average. A paired​ t-test was performed on data from a random selection of 15 of the marathons to determine if there was evidence to indicate that the​ women's winning wheelchair time is faster than the​ men's winning running​ time, on average. What must be true about the population of differences in the​ women's wheelchair winning times and​ men's winning times at this marathon for conclusions from the paired​ t-test to be​ valid? Choose the correct answer below. A. The distribution of sample means of the differences will be approximately normal if there are at least 30 years of data in the sample​ and/or if the population of differences in winning times for all years is normal. B. Because there were at least 5 years of​ observations, the distribution of sample means of the differences will be approximately normal by the Central Limit Theorem. C. Because the sample size is large​ enough, the distribution of differences for all years will be normal. D. Because of the small sample size of differences in winning times between the​ women's wheelchair winner and the​ men's running​ winner, the distribution of sample means of the differences cannot be normal.

Answer 1

A. The distribution of sample means of the differences will be approximately normal if there are at least 30 years of data in the sample​ and/or if the population of differences in winning times for all years is normal.

Explanation:

In other to perform a valid paired test, one of the conditions required is that, data for both groups must be approximately normal. To attain normality, the population distribution for the groups must be normal or based on the central limit theorem, the sample size must be large enough, usually n > 30. Hence, once either of the two conditions are met, the paired sample will be valid.