A recent study focused on the number of times men and women send a Twitter message in a day. The samples information is summarized below. Sample Size Sample Mean Population Standard Deviation
Men 25 23 5
Women 30 28 10

At the 0.01 significance level, we ask if there is a difference in the mean number of times men and women send a Twitter message in a day. Which of the following test statistics should be used to test this hypothesis?

a. z-statistic
b. t-statistic
c. p-statistic
d. df-statistic