The following 5 questions are based on thisinformation.
A random sample of 25 Apple (the company) customers who call AppleCare Support line had an average (X bar) wait time of 187 secondswith a sample standard deviation (s) of50 seconds. The goal is to construct a 90% confidence interval forthe average (μ) wait time of all Apple customers who call forsupport.
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 intervalestimation 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 is175 seconds. In light of the sample evidence and at the 10% levelof 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 estimatewill
Select one:
a. decrease
b. be zero
c. increase
d. stays the same
