What is the minimum sample size required to estimate a population mean with 90% confidence when the desired margin of error is D

The expression for the required minimum sample size is .

Step-by-step explanation:

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

The margin of error for this interval is:

Confidence level = 90%

α = 10%

Compute the critical value of z for α = 10% as follows:

 z = 1.645

*Use a z-table.

Compute the sample size required as follows:

Thus, the expression for the required minimum sample size is .