Mind On Statistics - Chapter 13 Worksheets With Answers Page 16
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32Chapter 13
Questions 81 to 85: A researcher wants to assess if there is a difference in the average age of onset of a certain
disease for men and women who get the disease. Let
= average age of onset for women and
= average age
1
2
of onset for men. A random sample of 30 women with the disease showed an average age of onset of 83 years, with
a sample standard deviation of 11.5 years. A random sample of 20 men with the disease showed an average age of
onset of 77 years, with a sample standard deviation of 4.5 years. Assume that ages at onset of this disease are
normally distributed for each gender, do not assume the population variances are equal, and use the conservative “by
hand” estimate for the degrees of freedom.
81. What are the appropriate null and alternative hypotheses?
0
A. H
:
= 0 and H
:
0
1
2
a
1
2
0 and H
B. H
:
:
= 0
0
1
2
a
1
2
C. H
:
= 0 and H
:
< 0
0
a
1
2
1
2
D. H
:
= 0 and H
:
> 0
0
1
2
a
1
2
KEY: A
82. What is the value of the test statistic?
A. t = 2.00
B. t = 2.33
C. t = 2.58
D. None of the above
KEY: C
83. What is the p-value?
A. p-value = 0.009
B. p-value = 0.018
C. p-value = 0.015
D. None of the above
KEY: B
84. For a significance level of
= 0.05, are the results statistically significant?
A. No, results are not statistically significant because the p-value < 0.05.
B. Yes, results are statistically significant because the p-value < 0.05.
C. No, results are not statistically significant because the p-value > 0.05
D. Yes, results are statistically significant because the p-value > 0.05.
KEY: B
85. Which of the following is an appropriate conclusion?
A. There is a statistically significant difference in average age at onset for men and women.
B. The difference is not statistically significant: there is not enough evidence to conclude the average ages at
onset are different.
C. The average age at onset for women is 6 years later than the average age at onset for men.
D. None of the above.
KEY: A
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