Question

How large a sample should be selected to provide a 95% confidence interval with a margin of error of 10 (to the nearest whole number)? Assume that the population standard deviation is 40.

Answer 1

Try this formula:

n = [(z-value * sd)/E]^2

With your data:

n = [(1.96 * 40)/10]^2

I'll let you finish the calculation. Remember to round the answer to the nearest whole number.

Answer 2

61.4656