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

20

step-by-step explanation:

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