Use the following for questions 8 9 are all employees

Use the following for questions 8 – 9:
Are all employees equally prone to having accidents? To investigate this hypothesis, a researcher
looked at a light manufacturing plant and classified a random sample of accidents by type and by
age of the employee.
Under 25
Age
25 or over
8. Here are the expected counts for this table under the null hypothesis that tests the
question stated above:
Under 25
Age
25 or over
What is the individual component of the chi-square statistic for the cell ―Under 25/Burn? ‖

© 2011 BFW Publishers The Practice of Statistics, 4/e- Chapter 11 529

9. A chi-square test for the above data gave a test statistic of 20.78. If we test at = 0.05 which
of the following is an appropriate conclusion?
10. A survey was conducted to investigate whether alcohol consumption and smoking
are related. In an SRS of 300 smokers, 196 said they had consumed alcohol at least once in
the past week. In an independent SRS of 300 non-smokers, 159 said they had consumed
alcohol in the past week. If p
s
is the proportion of smokers in the population who have had a
drink in the past week and p
ns
is the corresponding proportion of non-smokers, then a test of
the
hypotheses H
0
: p
s
p
ns
0 against the two-sided alternative produces a test statistic of
3.07 and a P -value of 0.002. If we had instead analyzed these results with a chi-square test
of homogeneity, which of the following would be the test statistic and P -value?
z =

530 The Practice of Statistics, 4/e- Chapter 11 © 2011 BFW Publishers

Part 2: Free Response
Show all your work. Indicate clearly the methods you use, because you will be graded on the
correctness of your methods as well as on the accuracy and completeness of your results and
explanations.
11. Are you more likely to be allergic to house dust mites if you are born in a certain
season? Recent research suggests this might be true. Below are the birth seasons of 500
randomly selected people who are allergic to house dust mites, along with the expected
proportion of people born in each season, based on data from the entire population. Do
these data provide evidence that people who suffer from this allergy have a different birth
season distribution? Support your conclusion with the appropriate statistical test.