Question

A set of solar batteries is used in a research satellite. The satellite can run on only one battery, but it runs best if more than one battery is used. The variance σ² of lifetimes of these batteries affects the useful lifetime of the satellite before it goes dead. If the variance is too small, all the batteries will tend to die at once. Why? If the variance is too large, the batteries are simply not dependable. Why? Engineers have determined that a variance of σ² = 23 months (squared) is most desirable for these batteries. A random sample of 28 batteries gave a sample variance of 14.6 months (squared). Using a 0.05 level of significance, test the claim that σ² = 23 against the claim that σ² is different from 23.

(f) Find a 90% confidence interval for the population variance. (Round your answers to two decimal places.)

lower limit
upper limit

(g) Find a 90% confidence interval for the population standard deviation. (Round your answers to two decimal places.)V

lower limit	months
upper limit	months

Answer 1