ENGRD2700
Basic Engineering Probability and Statistics
Spring 2009
Homework 10: Hypothesis Testing for Multiple Samples.
Hand in by 1:30 pm on Friday, April 24 in the ENGRD2700 dropbox.
Be sure to write your name and section number (1–6) on your homework.
Make sure that your homework pages are
stapled
together. This homework has 9 parts.
NOTE:
Your answers will be graded on the clarity of your writing as well as the correctness of the
answer. You must show your work to receive full credit. Any work that you submit must be your own.
1. Use the data of Devore (7e), Page 334, Exercise 7 to construct a 95% confidence interval for the
difference in mean Boredom Proneness Rating between men and women.
2. Consider the data of Devore (7e), Page 350, Exercise 36.
(a) Construct a 95% confidence interval for the difference in mean breaking load between Abraided
and Unabraided fabrics.
(b) What would the same interval be if we mistakenly thought that these were independent fabric
samples?
(c) Compute the correlation between the U and A samples.
3. Consider the data of Devore (7e), Page 342, Exercise 28 (also used in Page 363, Exercise 59). Find a
90% confidence interval for the ratio of the two variances. Now do the same for the ratio of the two
standard deviations.
4. Twentytwo students took an exam. They were divided randomly into two equal groups. Grader A
marked the scripts of one group of eleven, Grader B marked the other eleven. Here are their scores:
Student
1
2
3
4
5
6
7
8
9
10
11
Grader A
61
43
49
52
67
40
41
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 Spring '05
 STAFF
 Statistics, Normal Distribution, Standard Deviation, DeVore, Grader B.

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