Aresearch firm wants to compute an interval estimate with 90% confidence for the mean time to complete an employment test. assuming a population standard deviation of three hours, what is the required sample size if the error should be less than a half hour? select one: a. 196 b. 98 c. 10 d. 16

b. 98

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 M as such

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

In this problem, we have that:

So a sample of at least 98 is required.

The correct answer is:

b. 98

step-by-step explanation:

you can add the two numbers and divide the result by 2. or you can find the gap between the two numbers and add half of this to the smaller number.