Answer to Question #297442 in Mechanical Engineering for ajay

Question

The lifetime of 225 light bulbs is measured and the sample mean and sample variance are found to be 223 hr and 100 hr2 , respectively. (a) Find a 95% confidence interval for the mean lifetime. (b) Find a 95% confidence interval for the variance of the lifetime.

Answer 1

Sample mean=223hr

Sample variance=100hr²

a)

For 95%

223-2.92$\le$ 223$\le$ 223+5.62

220.08$\le$ 223$\le$ 228.62

b)

For 95%

87.3$\le$ 100$\le$ 112.7