(Solved): The time in hours for a worker to repair an electrical instrument is a Normally distributed random v ...

The time in hours for a worker to repair an electrical instrument is a Normally distributed random variable with a mean of

and a standard deviation of 50 . The repair times for 12 such instruments chosen at random are as follows:

Part a) Find a

confidence interval for

. For both sides of the bound, leave your answer with 1 decimal place.

.

Part b) Find the least number of repair times needed to be sampled in order to reduce the width of the confidence interval to below 29 hours. Show steps thx