A population has a standard deviation of 15.2. How large a sample must be drawn so that a 95% confidence interval for the population mean will have a margin error equal to 3.5?

Answer 1

Use a formula to find sample size.

Here is one:
n = [(z-value * sd)/E]^2
...where n = sample size, z-value = 1.96 for 95% confidence, sd = 15.2, E = 3.5, ^2 means squared, and * means to multiply.

Plug the values into the formula and finish the calculations. Round your answers to the next highest whole number.

I'll let you take it from here.