A production manager wishes to determine if there is a difference in the number of production units produced by the night shift and the day shift. A random sample of night and day shifts is selected, and the number of production units for each shift is recorded. The following statistics resulted:Day shift: sample mean = 27.4, standard deviation = 6.4, sample size = 60. Night shift: sample mean = 18.3, standard deviation = 5.9, sample size = 60.
A. Find a 90% confidence interval on the difference in the mean number of production units for the two shifts.
B. Calculate a 99% confidence interval for part A.
C. Compare the two confidence intervals in parts a and b, and comment on the length of the intervals.