Statistics in a Modern World 800
Homework 4 NAME:_________________________________

Homework 4 Exercises Assigned from Chapters 9-11 (20 pts.) due Fri., October 9 in Lecture.

CHAPTER 9

#6 (1 pt.) Using the data shown in Table 9.1 p.176, draw a bar graph presenting the information. Be sure to include all the components of a good statistical picture. [Do this directly to the right of the table shown.]

Kids Live With 1960 1980 1990
Father and mother 80.6% 62.3% 57.7%
Mother only 7.7% 18.0% 21.6%
Father only 1.0% 1.7% 3.1%
Father and stepmother 0.8% 1.1% 0.9%
Mother and stepfather 5.9% 8.4% 10.4%
Neither parent 3.9% 5.8% 4.3%

#10 (1 pt.) Use Table 9.3 p.177 to draw a pie chart illustrating the blood-type distribution for white Americans, ignoring the RH factor. [Do this directly to the right of the table shown.]
  White Americans   Black Americans
 
 
Blood Type Rh+ Rh-   Rh+ Rh-
A 38.8% 7.0%  26.0%2.0%
B 7.0% 1.0%  17.0%1.5%
AB 3.0% 0.6%  4.0%0.4%
O 37.0% 6.0%  45.0%4.0%

CHAPTER 10

#2 (1 pt.) It was observed that the correlation between husbands' and wives' heights, measured in millimeters, was 0.36. What would the correlation be if the heights were converted to inches?

#4 (2 pts.) Are each of the following pairs of variables likely to have a positive correlation or a negative correlation?

  1. Daily temperature at noon in New York City and in Boston. (i) positive (ii) negative
  2. Weight of a car and its mean gas mileage (mean miles per gal) (i) positive (ii)negative
  3. Hours of television watched and GPA for college students (i) positive (ii) negative
  4. Years of education and salary (i) positive (ii) negative

#5 (1 pt.) Suppose a weak relationship exists between two variables in a population. Which would be more likely to result in a statistically significant relationship between the two variables? (I) a sample of size 100 (II) a sample of size 10,000

#10 (a) (1 pt.) The regression line relating verbal SAT scores and GPA for the data exhibited in Figure 9.5 is GPA = 0.539 + (0.00362)(verbal SAT). Predict the average GPA for those with verbal SAT scores of 500.

#13. (1 pt.) Exercise 12 p. 197 reports a regression equation relating winning time in Olympic speed skating versus year for 1924 to 1998. Use one key word to tell why we should not use the regression equation to predict the winning time for the 2014 Winter Olympics.

CHAPTER 11

#3. (3 pts.) An article in Science News claimed that "evidence suggests that regular consumption of milk may reduce a person's risk of stroke, the third leading cause of death in the U.S." The claim was based on an observational study of 3150 men, and the article noted that the researchers "report strong evidence that men who eschew [give up] milk have more than twice the stroke risk of those who drink 1 pint or more daily." The article concluded by noting that "those who consumed the most milk tended to be the leanest and the most physically active."

  1. Circle the word or words that tell the explanatory variable.
  2. Underline the word or words that tell the response variable.
  3. Pick one of the seven reasons listed on page 207 which provides a good explanation for the relationship. (Circle it.) 1 2 3 4 5 6 7
    1. The explanatory variable is the direct cause of the response variable.
    2. The response variable is causing a change in the explanatory variable.
    3. The explanatory variable is a contributing but not sole cause of the resonse variable.
    4. Confounding variables may exist.
    5. Both variables may result from a common cause.
    6. Both variables are changing over time.
    7. The association may be nothing more than coincidence.

#4 (2 pts.) Iman (p. 505) presents data on how college students and experts perceive risks for 30 activities or technologies. Each group ranked the 30 activities. The rankings for the eight greatest risks, as perceived by the experts, are shown in Table 11.5.
Activity or Technology Experts' Rank Students' Rank
Motor vehicles 1 5
Smoking 2 3
Alcoholic Beverages 3 7
Handguns 4 2
Surgery 5 11
Motorcycles 6 6
X rays 7 17
Pesticides 8 4
  1. Prepare a scatterplot of the data, with students' ranks on the vertical axis and experts' ranks on the horizontal axis. [Do this directly to the right of the table shown.]
  2. Another technology listed was nuclear power, ranked first by the students and 20th by the experts. If nuclear power were added to the list, do you think the correlation between the two sets of rankings would increase or decrease?

#6 (1 pt.) Which one of the seven reasons for relationships (listed in #3 above) is supposed to be ruled out by designed experiments?

#12 (6 pts.) Suppose a positive relationship had been found between each of the following sets of variables. On p.207, seven potential reasons for such relationships are given (see #3 above). Circle the one of the seven reasons which is most likely to account for the relationship in each case.

  1. Number of deaths from automobiles and beer sales for each year from 1950 to 1990. 1 2 6 7
  2. Number of ski accidents and average wait time for the ski lift for each day during one winter at a ski resort. 1 2 5 7
  3. Stomach cancer and consumption of barbecued foods, which are known to contain carcinogenic (cancer-causing) substances. 1 2 6 7
  4. Self-reported level of stress and blood pressure. 2 3 6 7
  5. Amount of dietary fat consumed and heart disease. 2 3 5 7
  6. Twice as many cases of leukemia in a new high school, built near a power plant, than at the old high school. 2 4 5 7

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