Question

A 95% confidence interval for a population mean was reported to be 23,100 to 24,900. If the sample standard deviation is 5,808.26, what sample size was used in this study?

Answer 1

Formula:
CI95 = mean + or - (1.96)(sd)/√n

Mean = (23100 + 24900)/2 = 24000
Standard deviation = 5808.26

CI95 = 24000 + or - 900 --> gives you confidence interval of 23100 to 24900.

Therefore:
900 = (1.96)(sd)/√n
900 = (1.96)(5808.26)/√n

Solve for n. Round n to whole number.

I hope this will help.