A null hypothesis is that the mean nose lengths of men and women are the same. The alternative hypothesis is that men have a longer mean nose length than women. Which of the following is the correct way to state the null hypothesis?
A. Ho: p = 0.5
B. Ho: x1-x2 = 0
C. Ho: p1-p2 = 0
D. Ho: mu1-mu2 = 0