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Test 10B
AP Statistics
Name:
Directions:
Work on these sheets. Answer completely, but be concise.
A normal probability table is
attached.
1. In formulating hypotheses for a statistical test of significance, the null hypothesis is
often
A) a statement that there is “no effect” or “no difference.”
B) the probability of observing the data you actually obtained.
C) a statement that the data are all 0.
D) 0.05.
2. An agricultural researcher plants 25 plots with a new variety of corn. A 90% confidence
interval for the average yield for these plots is found to be 162.72 ± 4.47 bushels per
acre. Which of the following would produce a confidence interval with a smaller margin
of error than this 90% confidence interval?
A) planting only five plots rather than 25, since five are easier to manage and control.
B) planting 100 plots rather than 25.
C) computing a 99% confidence interval rather than a 90% confidence interval; the increase in
confidence indicates that we have a better interval.
D) none of the above.
3. A small company consists of 25 employees. As a service to the employees, the company arranges
for each to have a complete physical for free. Among other things, the weight of each employee is
measured; the mean weight is found to be 165 pounds. The population standard deviation is 20 pounds.
It is believed that a mean weight of 160
pounds would be normal for this group. To see if there is evidence that the mean weight
of the population of all employees of the company differs significantly from 160, the
hypotheses
H
0: μ = 160,
H
a: μ > 160 are tested. You obtain a
P
value of less than 0.1056. Which of
the following is true?
A) At the 5% significance level, you have proved that
H
0 is true.
B) You have failed to obtain any evidence for
H
a.
C) At the 5% significance level, you have failed to prove that
H
0 is true, and a larger sample
size is needed to do so.
D) None of the above.
4. The mean area μ of the several thousand apartments in a new development is advertised to be 1250
square feet. A tenant group thinks that the apartments are smaller than advertised. They hire an
engineer to measure a sample of apartments to test their suspicion. The appropriate null and alternative
hypotheses,
H
0 and
H
a, for μ
A) are
H
0: μ = 1250,
H
a: μ ¹ 1250.
B) are
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 Spring '11
 Smith
 Statistics, Probability

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