Question

The manager of a grocery store has selected a random sample of 100 customers. The average length of time it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the checkout time is 1 minute. Refer to Exhibit 8-2. If the confidence coefficient is reduced to .80, the standard error of the mean _____. a. becomes negative b. remains unchanged c. will increase d. will decrease

Answer 1

b. remains unchanged

Explanation:

Formula for standard error of mean is;

SE = σ/√n

From the above, we can see that the standard error of mean is independent of the confidence coefficient as it doesn't affect the SE.

Now, we are given that;

random sample; n = 100

Standard deviation; σ = 1

Thus;

SE = 1/√100

SE = 1/10

Now, even if the confidence coefficient is reduced, we can see that it has no impact on the standard error of mean.

Thus, SE remains unchanged.