In a manufacturing process a random sample of 49 bolts manufactured has a mean length of 1.24 inches with a standard deviation of .07 inches.use a normal disribution or a t-distribution to construct a 80% confidence interval for the mean.
A. Which distribution should be used to construct the 80%confidence level?
B. The 80% confidence interval is (?- , -?-) (round to two decimal places.)