A statistics practitioner would like to estimate a population mean to within 50 units with 99% confidence given that the population standard deviation is 250. What sample size should be used? b. Re-do part (a) changing the standard deviation to 50. c. Re-do part (a) using a 95% confidence leve

(a) 167

(b) 7

(c) 97

Step-by-step explanation:

The (1 - α)% confidence interval for the population mean μ is:

The margin of error is:

Then the formula to estimate the sample size is:

(a)

For 99% confidence interval the critical value of z is:

z = 2.58.

The standard deviation is, 250.

Compute the sample size as follows:

The sample size that should be used is 167.

(b)

Now the standard deviation is, 50.

Compute the sample size as follows:

The sample size that should be used is 7.

(c)

Now a 95% confidence level is used.

For 95% confidence interval the critical value of z is:

z = 1.96.

Compute the sample size as follows:

The sample size that should be used is 97.

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step-by-step explanation:

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