Question

A professor's sample estimated the standard deviation of missing assignments to be 3. You are researching the average missing assignments. You want to know how many people you should survey if you want to know, at a 90% confidence level, that the sample mean amount of missing assignments is within 1 assignments of the true mean number of missing assignments. Use a calculator to find the z- value that you should you use to calculate the 90% confidence level. Round your answer to three decimal places.

Answer 1

Here standard deviation is 3

Margin of Error is E=1

Now for 90% CI z value is 1.645 as P(-1.645<z<1.645)=0.90

Now we will find n using formula of E

So