Which level of confidence requires a larger sample size

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Reference no: EM13145881

In order to fairly set flat rates for auto mechanics, a shop foreman needs to estimate the average time it takes to replace a fuel pump in a car. Assume that the standard deviation of all times is 30 minutes.

a. Determine the minimum sample size he must select if he wants to be 90% confident that the true average time is within 10 minutes of the sample average?

b. Repeat part (a) using a 95% confidence interval.
(a) Which level of confidence requires a larger sample size? Explain.

Reference no: EM13145881

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