Question

The following 5 questions are based on this information.

A random sample of 25 Apple (the company) customers who call Apple Care Support line had an average (X bar) wait time of 187 seconds with a sample standard deviation (s) of 50 seconds. The goal is to construct a 90% confidence interval for the average (μ) wait time of all Apple customers who call for support.

Assume that the random variable, wait time of Apple customers (denoted by X), is normally distributed.

1) The standard error (SE) of X bar is

Select one:

a. 2

b. 10

c. 50

d. 37.4

2) The critical value (CV) needed for 90% confidence interval estimation is

Select one:

a. 1.28

b. 0.05

c. 1.71

d. 0.1

3) The 90% confidence interval estimate of μ is

Select one:

a. 187 ± 10

b. 187 ± 17.1

c. 187 ± 12.82

d. 187 ± 50

4) Suppose Apple claims that the average wait of a customer is 175 seconds. In light of the sample evidence and at the 10% level of significance,

Select one:

a. We can not reject Apple's claim

b. We can reject Apple's claim

5) If we increase the confidence level (1-α) from 0.90 to 0.95, the margin of error (ME) of the confidence interval estimate will

Select one:

a. decrease

b. be zero

c. increase

d. stays the same

Answer 1