CHAPTER 13
STATISTICAL SIGNIFICANCE FOR 2
×
2 TABLES
EXERCISE SOLUTIONS
13.1
A large sample is much more likely to result in a statistically significant relationship. The more data
available, the easier it is to rule out chance as an explanation for a relationship observed in the sample.
13.2
They are equivalent; the probability is usually set at 0.05.
13.3
a.
Yes, there is definitely a relationship in the sample. If there weren’t, the chisquare statistic would be
0 and the
p
value would be 1.0.
b.
There isn’t necessarily a relationship in the population. Using the usual significance level of 5%, in
about 5% of tests where there is no relationship in the population, the sample will produce a statistically
significant relationship.
c.
Yes, it is likely that there is a relationship in the population.
13.4
Null and alternative hypotheses are never about samples, they are always about populations. We know
whether there is a relationship in the sample because we have the data. We don’t have to make hypotheses
about samples.
13.5
They are expected if the null hypothesis is true.
13.6
a.
Yes.
b.
No.
c.
No.
d.
Yes.
e.
No.
f.
Yes.
13.7
a.
No.
b.
No, we do not talk about rejecting the alternative hypothesis in any case.
c.
No, the correct terminology is that we fail to reject the null hypothesis.
d.
No.
e.
Yes.
f.
No.
13.8
a.
No, 1.42 < 3.84.
b.
Yes, 4.5 > 3.84.
c.
Yes, 0.01 < 0.05.
d.
No, 0.15 > 0.05.
13.9
a.
The population is all registered voters over age 25. The two variables and their categories are
(1)Graduated from college (yes, no); (2)Voted in the last presidential election (yes, no).
b.
The population is people who were married during the 1970s and 1980s. The two variables and their
categories are (1)Smoker (yes, no) and (2)Got divorced (yes, no).
c.
The population is midsize cities in the United States. The two variables and their categories are (1)The
city’s median family income compared to median family income for the state (higher, lower); (2)One of
the 30 busiest airports in the country is within 50 miles of the city (yes, no).
13.10
a.
Null hypothesis is that there is no relationship between having graduated from college and voting in
the last presidential election for the population of registered voters over age 25. The alternative hypothesis
is that there is a relationship between having graduated from college and voting in the last presidential
election for voters over age 25.
b.
The null hypothesis is that there is no relationship between smoking and getting divorced for people
who were married during the 1970s and 1980s. The alternative hypothesis is that there is a relationship.
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 Spring '08
 SEIFRIEDTHOMASJ
 Null hypothesis, Statistical hypothesis testing, Statistical significance, Hangover

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