Ch.9-10 Review
CONFIDENCE INTERVALS
1. The drug Lipitor is meant to lower cholesterol levels. In a clinical trial of 863 patients who received 10mg
doses of Lipitor, 47 reported a headache as a side effect.
a) Construct a 90% confidence interval estimate of the proportion of Lipitor uses who will report a
headache as a side effect. Write a sentence to interpret the interval.
b) What is the point estimate for the proportion of Lipitor uses who will report a headache as a side effect?
2. A Gallup poll conducted on in June of 1950 asked 1,031 Americans, “How often do you bathe each week?”
Results of the survey indicated that x = 3.7 and s = 2.3.
a) Construct a 99% confidence interval estimate of the mean number of times Americans bathed each
week in 1950. Write a sentence to interpret the interval.
b) What is the point estimate for the mean number of times Americans bathed each week in 1950?
HYPOTHESIS TESTING
3. According to the American Hotel and Motel Association, the average price of a room in 1998 was $78.62 per
night. A lodging analyst claims that the value is now different. He conducts a study of 50 hotels and motels
and determines the mean price to be $80.04 with a standard deviation of $10.83. Test the claim that the
average price of a room is no longer $78.62. Use α = 0.01.
4. In a survey conducted by the American Animal Hospital Association, 40% of respondents stated that they talk
to their pets on the answering machine or telephone. A veterinarian actually believes that the percentage is
higher, so he randomly selected 150 pet owners and discovered that 64 of them spoke to their pet on the
answering machine or telephone. Test the veterinarian’s claim that more than 40% of pet owners speak to
their pets on the answering machine or telephone. Use α = 0.01.
OTHER:
5. Determine H0 and H1 then write the Type I and Type II errors for the following:
The mean score on the SAT Math exam is 516. A test preparation company states that the mean score
of students who take their course is higher than 516.
6. A sports commentator wants to estimate the proportion of Americans who follow professional football. What
sample size should be obtained if he wants to be within 3 percentage points with 95% confidence and he uses
a 2010 estimate of 0.53 obtained from a Harris Poll?
7. A sports commentator wants to estimate the proportion of Americans who follow professional football. What
sample size should be obtained if he wants to be within 2 percentage points with 90% confidence and he does
not use any prior estimates?
Ch.9-10 Review
ANSWERS:
1.
a) 1-Prop-ZInterval (.04176, .06717)
I am 90% confident that the true proportion of all Lipitor users that will report a headache as a side effect
is between .04176 and .06717.
b) pˆ 
2.
47
 0.05446
863
a) T-Interval (3.5151, 3.8849)
I am 99% confident that the true mean number of times that all Americans bathed each week in 1950 was
between 3.5151 and 3.8849 times per week.
b) x  3.7
3. T-Test
4. 1-Prop-ZTest
I. Ho: μ = 78.62
H1: μ ≠ 78.62 (claim) (2 tails)
II. α = 0.01 Critical Value(s) = ±2.678
II. Test Statistic = 0.93
IV. (picture) Bell-curve with 2 tails shaded at ±2.678.
I. Ho: p = .40
H1: p > .40 (claim) (right tail)
II. α = 0.01
Critical Value(s) = 2.33
III. Test Statistic = 0.67
IV. (picture) Bell curve with right tail shaded at 2.33.
TS is in the unshaded region on the right side.
V. P-value: 0.3584
VI. Do not Reject Ho
Conclusion: There is not sufficient evidence to
Conclude that the average price of a room is different
than $78.62 per night.
TS is in the unshaded region on the right side.
V. P-value = 0.2525
VI. Do not Reject Ho
Conclusion: There is not sufficient evidence to
conclude that more than 40% of pet owners
speak to their pets on the phone or answering machine.
5. Ho: μ = 516
H1: μ > 516
Type I: Reject that μ = 516 when μ = 516 is true.
Type II: Do not reject that μ = 516 when really μ > 516 is true.
2
 1.96 
6. n  (0.53  0.47)
  1063.269  (round up) 1,064
 0.03 
2
 1.645 
7. n  (0.25)
  1691.265  (round up) 1,692
 0.02 