Question

Among 420 randomly selected employees at a company, the mean number of hours of overtime worked per month is 10 hours and the standard deviation is 1.6. what is the margin of error, assuming a 99% confidence level?

A. 4.12

B. 0.01

C. 0.20

Answer 1

.20 aka C

Explanation:

Answer 2

To solve for the margin of error:

margin of error = critical value x standard error

To compute for the critical value:
1. compute alpha: α= 1 - (confidence level/100) = 1 - .99 = 0.01
2. Find the critical probability: p = 1 - α/2 = 1 - (0.01/2) = 0.995
3. Look for the z score at the z table, in this case it is 2.58. This is your critical value.

To compute for the standard error, the formula is:
standard error = standard deviation (σ) divided by √n = 1.6 / √420 = 0.0781

Now plug in the following in the formula:

margin of error: 2.58 * 0.0781 = 0.2014 or 0.20

The answer is letter C.