Question

Researchers studying two populations of wolves conducted a two-sample t-test for the difference in means to investigate whether the mean weight of the wolves in one population was different from the mean weight of the wolves in the other population. All conditions for inference were met, and the test produced a test statistic of t=2.771 and a p-value of 0.01.

Which of the following is a correct interpretation of the p-value?

a. Assuming that the mean weights of wolves in the populations are equal, the probability of obtaining a test statistic that is greater than 2.771 or less than −2.771−2.771 is 0.01.
b. Assuming that the mean weights of wolves in the populations are equal, the probability of obtaining a test statistic that is greater than 2.771 is 0.01.
c. Assuming that the mean weights of wolves in the populations are different, the probability of obtaining a test statistic that is greater than 2.771 or less than −2.771−2.771 is 0.01.
d. Assuming that the mean weights of wolves in the populations are different, the probability of obtaining a test statistic that is greater than 2.771 is 0.01.
e. Assuming that the mean weights of wolves in the populations are different, the probability of obtaining a test statistic that is less than 2.771 is 0.01.a

Answer 1

c. Assuming that the mean weights of wolves in the populations are different, the probability of obtaining a test statistic that is greater than 2.771 or less than −2.771 is 0.01.

Explanation:

Test if the sample means were different:

This means that we have a two-tailed test.

t=2.771 and a p-value of 0.01.

0.01 is the p-value of t = 2.771 multiplied by 2, as we have a two-tailed test(counting both more than 2.771 and less than -2.771). This represents the probabiility of obtaining a test statistic that is greater than 2.771 or less than −2.771 is 0.01, and the correct answer is given by option c.