A researcher wants to estimate the mean age of all Business Week readers at a 99% confidence level. The standard deviation of ages of all Business Week readors is nine years. The sample size that will yield a maximum error of estimate within three years of the population mean is at least:

A. 60
B. 97
C. 185
D. 8

A. 60

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.

We have to find:

n when . So

Dividing both sides by 3

We round up, so the correct answer is:

A. 60

828. all there is to it!

here, if you ever need with rounding (or other forms of arithmetic/math) again, use this:

thats the rounding one, but if you just click the top left, it shows you all the calculators you may need!

if you are saying purchasing 3 social media ads and one newspaper ad counts as one purchase then there are:

6 purchases

if you are asking how many of each then:

18 social media ads

6 newspaper ads