Question

In: Statistics and Probability

A service station advertises that customers will have to wait no more than 30 miniutes for...

A service station advertises that customers will have to wait no more than 30 miniutes for an oil change. A sample of 25 oil changes has a standard deviation of 5.2 minutes.

a) Find the 95% confidence interval of the population variance of the time spent waiting for oil change.

b) Find the 95% confidence interval of the population standard deviation of the time spent waiting for oil change.

Solutions

Expert Solution

At 95% confidence interval the critical values are = = 39.364

                                                                              = = 12.401

a) THe 95% confidence interval for is

(n - 1)s2/ < < (n - 1)s2/

= 24 * (5.2)^2/39.364 < < 24 * (5.2)^2/12.401

= 16.486 < < 52.331

b) The 95% confidence interval for is

sqrt(16.486) < < sqrt(52.331)

= 4.060 < < 7.234

orchestra answered 2 years ago
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