Introduction To Statistics And Data Analysis
6th Edition
ISBN: 9781337793612
Author: PECK, Roxy.
Publisher: Cengage Learning,
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Textbook Question
Chapter 2.2, Problem 31E
The financial aid advisor of a university plans to use a stratified random sample to estimate the average amount of money that students spend on textbooks each term. For each of the following proposed stratification schemes, discuss whether it would be worthwhile to stratify the university students in this manner. (Hint: Remember that it is desirable to create strata that are homogeneous.)
- a. Strata corresponding to class standing (freshman, sophomore, junior, senior, graduate student)
- b. Strata corresponding to field of study, using the following categories: engineering, architecture, business, other
- c. Strata corresponding to the first letter of the last name: A–E, F–K, etc.
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In a recent survey of a fair stratified random sample of the population,a question appeared as:Do you plan to vote in favor of the speed limit change?Yes/No.A scientist found the following number of responses per stratum:
Age
20-24
Age
25-29
Age
30-34
Yes
45
80
5
No
25
25
15
No response
25
10
55
(a)what are two reasons a respondent might not answer this question?
(b)what are the strata in this sample?
(c)If a person is picked at random from the sample,what is the probability that they are age 25-29 or did not respond to this question?
(d)If three people are picked at random from the sample,what is the probability that at least one did not respond to this question?
(e)If we assume there is no bias,what conclusion can be drawn about the population's opinion of the speed limit change?Justify your response
(f)How would your answer to (e) change if we found out that 90% of those who did not respond are actually against the change?
A mining company finds that daily lost-work injuries averages to 1.2. If the local union contract has a clause requiring that the mine be shut down as soon as three workers incur lost-work injuries, on what percentage of the days will the mine be operational throughout the day?
A statistics instructor asks each student in his classes to report how much the student spent on textbooks for the semester. The figures reported by students are shown below.
725
735
555
420
385
480
505
270
405
285
585
450
515
560
500
395
545
595
365
455
505
345
555
485
560
475
520
455
355
590
550
495
505
505
495
465
370
355
480
385
515
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410
485
560
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350
465
435
455
380
320
535
565
520
510
495
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650
490
295
555
540
565
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570
380
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390
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390
335
525
445
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555
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510
340
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Chapter 2 Solutions
Introduction To Statistics And Data Analysis
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