Question

9) (1 point) A recent report for a regional airline reported that the mean number of hours of flying time for its pilots is 56 hours per month. This mean was based on actual flying times for a sample of 49 pilots and the sample standard deviation was 9.5 hours.

2. Calculate a 90% confidence interval estimate of the population mean flying time for the pilots. Round your result to 4 decimal places.

( ,  )

3.Using the information given, what is the smallest sample size necessary to estimate the mean flying time with a margin of error of 1.75 hour and 90% confidence? Note: For consistency's sake, round your t* value to 3 decimal places before calculating the necessary sample size.

Choose n =

Answer 1

Answer:

2)

t critical value at 0.10 significance level with 48 df = 1.677

90% confidence interval for is

- t * S / sqrt(n) < < + t * S / sqrt(n)

56 - 1.677 * 9.5 / sqrt(49) < < 56 + 1.677 * 9.5 / sqrt(49)

53.8438 < < 58.1561

90% CI is ( 53.8438 , 58.1561 )

3)

Sample size = (t * S / sqrt(n) )

= ( 1.677 * 9.5 / 1.75)2

= 82.877

Sample size = 83 (Rounded up to nearest integer)

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