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Hypothesis Testing
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Drug Testing of Job Applicants. In 1990, 5.8% of job applicants who were tested for
drugs failed the test. At the 0.01 significance level, test the claim that the failure rate is
now lower if a simple random sample of 1520 current job applicants results in 58 failures
(based on data from the American Management Association). Does the result suggest
that fewer job applicants now use drugs? [NOTE: Both examples are from the 8th
edition of Elementary Statistics by Triola. Publisher: Pearson/Addison-Wesley.
Hypothesis Testing
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Mean Time for 4-Year
Degree. Kim is a high
school senior who is
concerned about
attending college
because she knows that
many college students
require more than four
years to earn a
bachelor’s degree. At
the 0.10 significance
level, test the claim of
her guidance counselor,
who states that the
mean time is greater
than 5 years. Sample
data consist of a mean
of 5.15 years and a
standard deviation of
1.68 years fro 80
randomly selected
college graduates
(based on data from the
National Center for
Education Statistics).
Hypothesis Testing
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Heights of Women.
According to Gordon,
Churchill, et al., women have
heights with a mean of 64.1
in. and a standard deviation
of 2.52 in. Using the sample
of heights of women in Data
Set 1 in Appendix B, test the
claim that the standard
deviation is 2.52 in. Use a
0.05 significance level. When
designing car seats for
women, what would be a
consequence of believing
that heights of women vary
less than they really vary?
From Data Set 1, we find the
sample mean to be 63.195
in. and the sample standard
deviation to be 2.741228 in.
Testing the claim that the
standard deviation in heights
is equal to 2.52 in. yields the
conclusion that we should
fail to reject the null
hypothesis. Therefore, the
“sample does not provide
enough evidence to reject
the claim” that the standard
deviation is 2.52 in.