Question

How many commuters must be randomly selected to estimate the mean driving time of Chicago commuters? We want 98% confidence that the sample mean is within 4 minutes of the population mean, and the population standard deviation is known to be 12 minutes. 25 35 49 60

Answer 1

49

Explanation:

Margin of error = critical value × standard error

ME = CV × SE

The critical value at 98% confidence is z = 2.326.

Standard error is SE = σ / √n.

4 = 2.326 × 12 / √n

n = 49