6) A random sample of n = 25 students participated in a study to determine whether keyboard skills are improved by taking a typing
course. The typing speed of each student was recorded at the start of the course and again at the end of the course. The mean
difference for the sample is xd - 32, with a standard deviation of sd - 10. What is the 99% confidence interval for the mean
difference in typing speed?
A)
(25.818, 38.182)
B)
(26.406, 37.594)
(26.850, 37.150)
D)
(27.016, 36.984)