If you want to be 95% confident of estimating the population mean to within a sampling error of plus or minus3 and the standard deviation is assumed to be 20, what sample size is required? The sample size required is

The sample size required is at least 171

Step-by-step explanation:

We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of .

So it is z with a pvalue of , so

Now, find the margin of error M as such

In which is the standard deviation of the population and n is the size of the sample.

What sample size is required?

A samle size of at least n is required, in which n is found when

So

Rouding up

The sample size required is at least 171

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step-by-step explanation: