STAT
251G
Online
Class
Exam
3 Part 2
Name___________________________________
Date__________________
1. A food snack manufacturer samples 11
bags of pretzels off the assembly line and weighs their contents. If the sample mean is 13.2 oz. and the sample
standard deviation is 0.60 oz., find the 95% confidence interval of the true
mean. Show all work.
2. A random sample of
magnesium concentrations (in parts per million, or ppm) in ground water from
various locations follows. Estimate the mean concentration of magnesium in ppm
with 90% confidence. Show all work. You may use your calculator to find the mean
and standard deviation.
45
104
16
102
48
58
9
110
61
16
57
90
70
123
81
117
40
5
50
59
3. A
survey of 800 women shoppers found that 17% of them shop on impulse. What is the 98% confidence interval for the
true proportion of women shoppers who shop on impulse?
4. A manufacturer claims that its
televisions have an average lifetime of at least five years (60 months) with a population
standard deviation of seven months.
Eighty-one televisions were selected at random, and the average lifetime
was found to be 59 months. With ? = 0.05, is the manufacturer’s claim
supported? Conduct five-step hypothesis
testing.
5.
Science fiction novels average 310 pages in length. The average length of 14 randomly chosen
novels written by I. M. Wordy was 375 pages in length with a standard deviation
of 40. At .png”> = .05, are Wordy’s
novels significantly longer than the average science fiction novel?
Conduct
five-step hypothesis testing.
6.
Two allergists recorded the main area of
allergy for new patients during a month.
At .png”>, test the claim that the allergy diagnosis and the doctor
that treated the patients are independent.
Allergies
Pollen
Food
Mold
Pets
Doctor 1
8
6
5
7
Doctor 2
34
6
6
24
7. From the Data Bank in Appendix D,
choose two variables that you think might be related, such as exercise and weight,
or IQ and educational level.
Performa
complete correlation and regression analysis.
Use Minitab or Excel to do the calculations and the graphs, but you must
still conduct the hypothesis testing.
a. Draw a scatterplot
b. Compute the correlation coefficient
c. Use hypothesis testing to determine if
r is significant.
d. Find the regression line if r is
significant.
e. Summarize the results, include your
personal reaction to the results.
8. Suppose a school superintendent reads an
article which states that the overall mean score for the SAT is 910. He does
some research and collects data on a sample of his students. He discovered that the average is 960. The superintendent calls the local newspaper
to report that his students have scored much higher than the national
average. Is he correct? Explain your reasoning. What else should be considered in his claim.
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