Question

A survey of 37 randomly selected iPhone owners showed that the purchase price has a mean of $670 with a sample standard deviation of $34. (Use z Distribution Table.)

1. Compute the standard error of the sample mean. (Round your answer to the nearest whole number.)

2. Compute the 99% confidence interval for the mean. (Use t Distribution Table.) (Round your answers to 3 decimal places.)

Answer 1

Sample size, n = 37

mean = $670

sample standard deviation = s = $34

Compute the standard error of the sample mean.

Compute the 99% confidence interval for the mean.

At 99% confidence interval and df = n - 1 = 37 - 1 = 36

t_c = 2.7195

The 99% confidence interval is given by:

CI = ( 670 - 15.2, 670 +15.2)

CI = ( 654.8, 685.2 )