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Moore et al - The Basic Practice of Statistics 7/e (Homework)

James Finch

Statistics, section 2, Fall 2019

Instructor: Dr. Friendly

Current Score : 3 / 43

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

Last Saved : n/a Saving...  ()

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  • Instructions

    Moore’s data analysis approach in The Basic Practice of Statistics 7th edition, published by W.H. Freeman, moves students away from formulas and number-crunching, focusing instead on how working statisticians in a variety of fields collect and analyze data, and use the results to tackle real-world problems. The WebAssign component for this text engages students with immediate feedback, an interactive eBook with online resources, and a question bank of end-of-section exercises.

    All questions include a link to the eBook.

    Question 1 includes a graph with randomized values to provide students with a varying experience.

    Question 4 allows a student to enter their equation values individually for potential partial credit.

    Questions 5 and 7 provide links to probability tables found in the textbook’s appendix and the grading accepts answers found using either tables or software.

    Question 6 is structured to allow students to build the full probability statement.

    Question 7 has a two answer box structure to mimic the textbook’s presentation of confidence intervals.

    Question 8 demonstrates the format for grading stem and leaf plots with multiple answer blanks.

    Question 9 gives a data set presented as a full table along with a link to access the original data set file.

    Question 10 demonstrates an ANOVA table layout with answer boxes.

    Question 11 features an answer box that allows students to enter their model using variables and subscripts.

    View the complete list of WebAssign questions available for this textbook. This demo assignment allows many submissions and allows you to try another version of the same question for practice wherever the problem has randomized values.

Assignment Submission

For this assignment, you submit answers by question parts. The number of submissions remaining for each question part only changes if you submit or change the answer.

Assignment Scoring

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1. –/0 points MBasicStat7 3.E.017. My Notes
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The figure below shows a Normal curve.
WebAssign Plot
What is the mean of this distribution?
(No Response)
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2. 0/3 points  |  Previous Answers MBasicStat7 4.E.026. My Notes
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Some studies have suggested that a nightly glass of wine may not only take the edge off a day but also improve health. Is wine good for your health? A study of nearly 1.3 million middle-aged women examined wine consumption and the risk of cancer. The researchers were interested in how risk changed as wine consumption increased. Risk is based on cancer rates in drinkers relative to cancer rates in nondrinkers in the study, with higher values indicating greater risk. In particular, a value greater than 1 indicates a greater cancer rate than that of nondrinkers. Wine intake is the mean wine intake, in grams of alcohol per day (1 glass of wine is approximately 10 grams of alcohol), of all women in the study who drank approximately the same amount of wine per week. Here are the data (for drinkers only).
Wine intake x
(grams per day) 		2.5 9.0 15.5 25.5
Relative risk y 1.00 1.14 1.15 1.22
(a) Make a scatterplot of these data. Based on the scatterplot, do you expect the correlation to be positive or negative? Near ±1 or not?
     Incorrect: Your answer is incorrect.

(b) Find the correlation r between wine intake and relative risk. (Round your answer to four decimal places.)
r = Incorrect: Your answer is incorrect. seenKey

0.9223

Do the data show that women who consume more wine tend to have higher relative risks of cancer?
    
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3. 1/3 points  |  Previous Answers MBasicStat7 4.E.035. My Notes
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Changing the units of measurement can dramatically alter the appearance of a scatterplot. Examine the data on percent body fat and preferred amount of salt below.
Preferred amount
of salt x 		0.2 0.3 0.4 0.5 0.6 0.8 1.1
Percent body fat y 20 31 22 31 36 23 31
In calculating the preferred amount of salt, the weight of the salt was in milligrams. A mad scientist decides to measure weight in tenths of milligrams. The same data in these units are as follows.
Preferred amount
of salt x 		2 3 4 5 6 8 11
Percent body fat y 20 31 22 31 36 23 31
(a) Make a plot with the x axis extending from 0 to 12 and the y axis from 15 to 40. Plot the original data on these axes. Then plot the new data using a different color or symbol. The two plots look very different.

Correct: Your answer is correct.

(b) Nonetheless, the correlation is exactly the same for the two sets of measurements. Why do you know that this is true without doing any calculations?
     Incorrect: Your answer is incorrect.

Find the two correlations to verify that they are the same. (Round your answer to three decimal places.)
r =
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4. –/5 points MBasicStat7 5.E.037. My Notes
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How strongly do physical characteristics of sisters and brothers correlate? Here are data on the heights (in inches) of 11 adult pairs.
Brother 72 66 66 64 70 71 70 73 72 65 66
Sister 69 64 65 63 65 62 65 64 66 59 62
(a) Use your calculator or software to find the correlation. (Round your answer to three decimal places.)
r =

Give the least-squares line for predicting sister's height from brother's height. (Round your answer to three decimal places.)
ŷ = + x

Make a scatterplot that includes this line. (Do this on paper. Your instructor may ask you to turn in this work.)

(b) Damien is 66 inches tall. Predict the height of his sister Tonya. (Round your answer to one decimal place.)
ŷ = inches

Based on the scatterplot and the correlation r, do you expect your prediction to be very accurate? Why? (Select all that apply.)

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5. –/1 points MBasicStat7 12.E.054. My Notes
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How many close friends do you have? Suppose that the number of close friends adults claim to have varies from person to person with mean μ = 9 and standard deviation σ = 2.5. An opinion poll asks this question of an SRS of 1100 adults. We will see later that in this situation the sample mean response x has approximately the Normal distribution with mean 9 and standard deviation 0.075. What is P(8.9 ≤ x ≤ 9.1), the probability that the sample result x estimates the population truth μ = 9 to within ±0.1? (Round your answer to three decimal places.)


You may need to use the appropriate Appendix Table to answer this question.
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6. 2/4 points  |  Previous Answers MBasicStat7 13.E.009. My Notes
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Suppose that 11% of adults belong to health clubs, and 49% of these health club members go to the club at least twice a week. What percent of all adults go to a health club at least twice a week? Write the information given in terms of probabilities and use the general multiplication rule. (Let H be the event that an adult belongs to a club, and T be the event that he/she goes at least twice a week. Use 3 decimal places.)
P( ) = =

About % of all adults go to health clubs at least twice a week.
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7. –/4 points MBasicStat7 16.E.010. My Notes
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An SRS of 520 high school seniors gained an average of x = 11 points in their second attempt at the SAT Mathematics exam. Assume that the change in score has a Normal distribution with standard deviation σ = 48. (Round your answers to two decimal places.)
(a) Find a 90% confidence interval for μ based on this sample.
to

(b) What is the margin of error for 90%?


(c) Suppose we had an SRS of just 130 high school seniors. What would be the margin of error for 90% confidence?

You may need to use the appropriate Appendix Table to answer this question.
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8. –/7 points MBasicStat7 16.E.027. My Notes
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Sulfur compounds cause "off-odors" in wine, so winemakers want to know the odor threshold, the lowest concentration of a compound that the human nose can detect. The odor threshold for dimethyl sulfide (DMS) in trained wine tasters is about 25 micrograms per liter of wine (µg/l). The untrained noses of consumers may be less sensitive, however. Here are the DMS odor thresholds for 10 untrained students.
32 31 44 35 22 33 33 30 20 22
(a) Assume that the standard deviation of the odor threshold for untrained noses is known to be σ = 6 µg/l. Briefly discuss the other two "simple conditions," using a stemplot to verify that the distribution is roughly symmetric with no outliers. (Enter your answers from smallest to largest. Enter NONE in any unused answer blanks.)
Stems Leaves
2
2
3
3
4

(b) Following the four-step process, give a 95% confidence interval for the mean DMS odor threshold among all students. (Round your answers to two decimal places.)
to µg/l
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9. –/2 points MBasicStat7 26.E.008. My Notes
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We often describe our emotional reaction to social rejection as "pain." Does social rejection cause activity in areas of the brain that are known to be activated by physical pain? If it does, we really do experience social and physical pain in similar ways. Psychologists first included and then deliberately excluded individuals from a social activity while they measured changes in brain activity. After each activity, the subjects filled out questionnaires that assessed how excluded they felt. Below are data for 13 subjects. (Data set may be found here.)
Subject Social distress Brain activity
1 1.26 −0.055
2 1.85 −0.040
3 1.10 −0.026
4 2.50 −0.017
5 2.17 −0.017
6 2.67 0.017
7 2.01 0.021
8 2.18 0.025
9 2.58 0.027
10 2.75 0.033
11 2.75 0.064
12 3.33 0.077
13 3.65 0.124
The explanatory variable is "social distress" measured by each subject's questionnaire score after exclusion relative to the score after inclusion. (So values greater than 1 show the degree of distress caused by exclusion.) The response variable is change in activity in a region of the brain that is activated by physical pain. Negative values show a decrease in activity, suggesting less distress.

The scatterplot below shows a positive linear relationship. The research report gives the correlation r and the P-value for a test that r is greater than 0.
WebAssign Plot
What are r and the P-value? (You can use Table E or you can get more accurate P-values for the correlation from regression software.)
    

What do you conclude about the relationship?
    
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10. –/12 points MBasicStat7 27.E.014. My Notes
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Do high school students from different racial/ethnic groups have different attitudes toward mathematics? Measure the level of interest in mathematics on a 5-point scale for a national random sample of students. Here are summaries for students who were taking math at the time of the survey.
Racial/ethnic group n x s
African American 814 2.64 1.37
White 1852   2.25 1.34
Asian/Pacific Islander 661 2.65 1.29
Hispanic 887 2.50 1.27
Native American 200 2.50 1.27
Calculate the ANOVA table and the F statistic. (Round your answers for SS, MS, and F to two decimal places.)

Source of variation df SS MS F
Groups
Error
Total

Show that there are significant differences among the mean attitudes of the give groups. (Round your answer to four decimal places.)
P-value =

What explains the small P-value?
    

Do you think the differences are large enough to be important?
    
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11. –/1 points MBasicStat7 29.E.016. My Notes
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Suppose that you are designing a study to investigate the relationship between height and weight for boys and girls.

Let y be height, x1 be weight, and x2 be an indicator variable for gender. β1 is the slope (the rate at which height changes in response to changes in weight), β0 is the intercept for boys (or girls), and (β0 + β2) is the intercept for girls (or boys). β0 and β1 are the intercept and slope for the boys (or girls), and (β0 + β2) and (β1 + β3) are the intercept and slope for girls (or boys).

Specify a model with two regression lines that could be used to predict height separately for boys and for girls.
μy =
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