The Cycle Times for an Electroplating Machine Are Believed to Be

Multiple Choice

The cycle times for an electroplating machine are believed to be normally distributed.Twenty-one plating operations are randomly sampled, and cycle times are recorded.The sample average cycle time is 10.21 min, with a standard deviation of 0.59 min.What is a 95% confidence interval for the mean cycle time on this machine?

A) (9.958, 10.462)
B) (9.941, 10.479)
C) (8.979, 11.441)
D) (9.911, 10.509)