In Class Review
Chapters 7-9
1)
A certain lottery claims that 10% of its tickets wins some prize. A sample of 50
tickets had 3 winners. Test the claim using  = 0.01.
2)
A copying machine is advertised as making at least 25,000 copies before
requiring service. A consumer group wants to test this claim. Thirty randomly
selected customers had a mean of 24,850 copies with a standard deviation of 380
copies. Test the advertising claim using  = 0.01.
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3)
A morning Algebra class took a final exam with the following results: the mean
score was 81.2 points and the standard deviation of the sample was 10.4 points.
For a class taking the same test that evening the mean was 77.8 points with a
standard deviation of 10.6 points. There were 27 students in each class. Do these
samples support the claim that mean scores are higher for morning classes?
Assume the population variances are not equal and test using  = 0.05.
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4)
A car gets a mean of 18 miles per gallon. Using  = 0.01, test a mechanic’s claim
that a cheaper grade of gasoline makes a difference in the gas mileage. A sample
of 25 fill-ups with the cheaper gas got a mean of 17.8 mpg and a standard
deviation of 0.6 mpg.
5)
For the following data, x represents the number of alcoholic drinks consumed,
and Y represents the score on a dexterity test.
a) Graph the scatter plot of the data, labeling the axes appropriately.
X
2
1
3
4
2
1
5
6
Y
15
18
11
7
10
16
5
2
3
b) Given r = -0.959, test the significance of the correlation coefficient at the 0.05
level, giving your summary describing how the number of drinks is related to the
score on the dexterity test.
c) Find the equation of the regression line given the slope is -2.917 and the y
intercept is 19.25. Graph the regression line on the scatter plot.
d) Predict how many drinks a person who scored 12 on the dexterity test has
consumed.
e) Predict the test score for a person who has consumed 3 drinks.
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