A bank manager wishes to estimate the mean waiting time spent by customers at his bank. He knows from previous experience that the standard deviation is about 4.0 minutes. If he desires a 90 percent confidence interval estimate and wishes to have a margin of error of 1 minute, the required sample size will be approximately 143.

Question

Quizplus · Accepted Answer

The required sample size for estimating a mean with a specified margin of error (E), given the population standard deviation (σ) and desired confidence level (Z), is calculated using the formula $n = \left(\frac{Z\sigma}{E}\right)^2$. For a 90% confidence level, the Z value is approximately 1.645. Plugging in the values: $n = \left(\frac{1.645 \times 4}{1}\right)^2 = \left(6.58\right)^2 = 43.2964$, which rounds to approximately 43, not 143.

A Bank Manager Wishes to Estimate the Mean Waiting Time