In a Manufacturing Process a Random Sample of 9 Bolts

Multiple Choice

In a manufacturing process a random sample of 9 bolts manufactured has a mean length of 3cm with a standard deviation of .3cm.Assuming bolt length is normally distributed,what is the 95% confidence interval for the true mean length of the bolt?

A) 2.804 to 3.196
B) 2.308 to 3.692
C) 2.770 to 3.231
D) 2.412 to 3.588
E) 2.814 to 3.186