Additional Problems
1.
Fowle Marketing Research bases charges to a client on the assumption that telephone surveys can be completed in
an average time of 15 minutes or less. If a longer time is necessary, a premium rate is charged.
A sample of 35 survey times was taken and the data is in the dataset
Fowle.xls
, which is in the "Some Data" folder on
the course D2L site. From past studies, Fowle assumes
the population standard deviation of survey times is known
and is equal to 4 minutes
.
Which of the following is the null hypothesis for a test of the assumption that the company makes in setting its rates?
(Highlight or circle the correct answer.)
0
0
0
0
0
0
A.
:
15
B.
:
15
C.
:
15
D.
:
15
E.
:
15
F.
:
15
H
X
H
H
H
H
H
Is this a z-test or a t-test? T-test
Based on the rejection region, this is a RIGHT-
tailed test. (Enter "right", "left", or "two".)
For alpha = .01, the rejection region is defined by the critical value(s) 2.3263
(Enter out to 4 decimal places.), which
comes from the NORMAL
("normal" or "t") distribution.
The value of the test statistic is 22.1970
(Enter the value out to 4 decimal places.)
What is the p-value for this test? 0.000
(Enter the value out to 4 decimal places.)
Conclusion: The sample data provides evidence to REJECT ("support" or "reject") the null hypothesis. This indicates
the company is probably WRONG ("right" or "wrong") in its assumption.
2.
Suppose the cost of a VS2 clarity, H color one-carat diamond from Diamond Source USA is $5600. A midwestern
jeweler makes calls to a sample of 25 dealers in the diamond district in New York City to see if the average price of
diamonds there differs from $5600. The price quotes are collected in the dataset
Diamonds.xls
, which is in the
"Some Data" folder on the course D2L site.
Which of the following is the null hypothesis for the question being investigated by the jeweler?
(Highlight or circle the
correct answer.)
0
0
0
0
A.
:
5600
B.
:
5600
C.
:
5600
D.
:
5600
E.
:
5600
A
H
X
H
H
H
H
Is this a z-test or a t-test? T-test
Based on the rejection region, this is a TWO-tailed
test. (Enter "right", "left", or "two".)
For alpha = .05, the rejection region is defined by the critical value(s) -2.0639 AND 2.0639
(Enter out to 4 decimal
places.), which comes from the T
("normal" or "t") distribution.
The value of the test statistic is 2.2591
(Enter the value out to 4 decimal places.)
What is the p-value for this test? 0.0332
(Enter the value out to 4 decimal places.)
Conclusion: The sample data provides evidence to REJECT ("support" or "reject") the null hypothesis. This indicates
the true mean is probably DIFFERENT ("the same" or "different").
