statistics
posted by dean .
A woman and her son are debating about the average length of a preacher's sermons on Sunday
morning. Despite the mother's arguments, the son thinks that the sermons are more than twenty minutes.
For one year, he has randomly selected 12 Sundays and found an average time of 26.42 minutes with a
standard deviation of 6.69 minutes. Assuming that the population is normally distributed and using a 0.05
level of significance, he wishes to determine whether he is correct in thinking that the average length of
sermons is more than 20 minutes. What is the test statistic?
A. –3.32
B. 3.32
C. 0.95
D. 6.69

Z = (scoremean)/SEm
SEm = SD/√n
I'll let you do the calculations.