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Moore - Intro to the Practice of Statistics 8e (Homework)

James Finch

Statistics, section 2, Fall 2019

Instructor: Dr. Friendly

Current Score : 10 / 26

Due : Sunday, January 27, 2030 23:30 EST

Last Saved : n/a Saving...  ()

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4/4 3/3 –/3 –/1 –/1 3/3 –/11
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10/26 (38.5%)

  • Instructions

    With this updated new edition, the market-leading Introduction to the Practice of Statistics 8th edition by David S. Moore, George P. McCabe, and Bruce Craig remains unmatched in its ability to show how statisticians actually work. Its focus on data analysis and critical thinking, step-by-step pedagogy, and applications in a variety of professions and disciplines make it exceptionally engaging to students learning core statistical ideas. The WebAssign component for this text extends and enhances the classroom experience for instructors and students. It includes the entire eBook in a user-friendly online format, along with a variety of additional learning resources.

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1. 4/4 points  |  Previous Answers MIntroStat8 2.E.034. My Notes
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4/4
 
A study of reading ability in schoolchildren chose 60 fifth-grade children at random from a school.† The main purpose of this study was to ask whether schoolchildren can estimate their own reading ability. The researchers had the children's scores on a test of reading ability. They asked each child to estimate his or her reading level, on a scale from 1 (low) to 5 (high). The figure shown below is a scatterplot of the children's estimates (response) against their reading scores (explanatory).
(a) What explains the "stair-step" pattern in the plot?
     Correct: Your answer is correct.

(b) Is there an overall positive association between reading score and self-estimate?
    

(c) There is one clear outlier. What is this child's self-estimated reading level?
Correct: Your answer is correct.

Does this appear to over- or underestimate the level as measured by the test?
     Correct: Your answer is correct.

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2. 3/3 points  |  Previous Answers MIntroStat8 2.E.060. My Notes
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1/1 1/1 1/1
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3/3
 
Each of the following statements contains a blunder. Explain in each case what is wrong.
(a) "There is a high correlation between the gender of American workers and their income."
     Correct: Your answer is correct.

(b) "We found a high correlation
(r = 1.04)
 between students' ratings of faculty teaching and ratings made by other faculty members."
     Correct: Your answer is correct.

(c) "The correlation between planting rate and yield of corn was found to be
r = 0.27
 bushel."
     Correct: Your answer is correct.

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3. –/3 points MIntroStat8 2.E.087. My Notes
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–/3
 
The data from data408.dat contains information on 78 seventh-grade students. We want to know how well each of IQ score and self-concept score predicts GPA using least-squares regression. We also want to know which of these explanatory variables predicts GPA better. Give numerical measures that answer these questions. (Round your answers to three decimal places.)
(Regressor: IQ) R 2


(Regressor: Self-Concept) R 2

Which variable is the better predictor?
    

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4. –/1 points MIntroStat8 2.E.090. My Notes
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–/1
 
A study of class attendance and grades among first-year students at a state university showed that in general students who attended a higher percent of their classes earned higher grades. Class attendance explained 49% of the variation in grade index among the students. What is the numerical value of the correlation between percent of classes attended and grade index? (Enter your answer to one decimal place.)

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5. –/1 points MIntroStat8 2.E.106. My Notes
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–/1
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–/1
 
The effect of a lurking variable can be surprising when individuals are divided into groups. In recent years, the mean SAT score of all high school seniors has increased. But the mean SAT score has decreased for students at each level of high school grades (A, B, C, and so on). Explain how grade inflation in high school (the lurking variable) can account for this pattern. A relationship that holds for each group within a population need not hold for the population as a whole. In fact, the relationship can even change direction.

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6. 3/3 points  |  Previous Answers MIntroStat8 2.E.140. My Notes
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3/3
 
A study showed that women who work in the production of computer chips have abnormally high numbers of miscarriages. The union claimed that exposure to chemicals used in production caused the miscarriages. Another possible explanation is that these workers spend most of their work time standing up. Illustrate these relationships in a diagram by selecting the appropriate variable placement below.
WebAssign Plot Correct: Your answer is correct. Correct: Your answer is correct. Correct: Your answer is correct.

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7. –/11 points MIntroStat8 2.E.175. My Notes
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–/11
 
Mountain View University has professional schools in business and law. Here is a three-way table of applicants to these professional schools, categorized by gender, school, and admission decision.
Business Law
Admit Admit
Gender Yes No Gender Yes No
Male 388 200 Male 87 101
Female 203 99 Female 191 186
(a) Make a two-way table of gender by admission decision for the combined professional schools by summing entries in the three-way table.
Admit Deny
Male
Female

(b) From your two-way table, compute separately the percents of male and female applicants admitted. Male applicants are admitted to Mountain View's professional schools at a higher rate than female applicants. (Round your answers to one decimal place.)
Male %
Female %

(c) Now compute separately the percents of male and female applicants admitted by the business school and by the law school. (Round your answers to one decimal place.)
Business Law
Male % %
Female % %

(d) Explain carefully, as if speaking to a skeptical reporter, how it can happen that Mountain View appears to favor males when this is not true within each of the professional schools.

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