Chapter 1 Problems

1.23 Medical students. Students who have finished medical school are assigned to residencies in hospitals to receive further training in a medical specialty. Here is part of a hypothetical data base of students seeking residency positions. USMLE is the student's score on Step 1 of the national medical licensing examination.

Name Medical school Sex Age USMLE Specialty sought
Abrams, Laurie Florida F 28 238 Familty medicine
Brown, Gordon Meharry M 25 205 Radiology
Cabrera, Maria Tufts F 26 191 Pediatrics
Ismael, Miranda Indiana F 32 245 Internal medicine
  1. What individuals does this data set describe?
  2. In addition to the student's name, how many variables does the data set contain? Which of these variables are categorical and which are quantitative?

1.26 Facebook and MySpace audience Although most social-networking Web sites in the United States have fairly short histories, the growth of these sites has been exponential. By far, the two most visited social-networking sites are Facebook.com and MySpace.com. Here is the age distribution of the audience for the two sites in December 2009. FACEBOOK

  1. Draw a bar graph for the age distribution of Facebook visitors. Do the same for MySpace, using the same scale for the percent axis.
  2. Describe the most important difference in the age distribution of the audience for Facebook and MySpace. How does this difference show up in the bar graphs? Do you think it was important to order the bars by age to make the comparison easier?
  3. Explain why it is appropriate to use a pie chart to display either of these distributions. Draw a pie chart for each distribution. Do you think it is easier to compare the two distributions with bar graphs or pie charts? Explain your reasoning.

1.35 Where are the nurses? The following spreadsheet gives the number of active nurses per 100,000 people in each state. NURSES

  1. Why is the number of nurses per 100,000 people a better measure of the availability of nurses than a simple count of the number of nurses in a state?
  2. Make a histogram that displays the distribution of nurses per 100,000 people. Write a brief description of the distribution. Are there any outliers? If so, can you explain them?

Chapter 2 Problems

2.25 Incomes of college grads. According to the Census Bureau's 2010 Current Population Survey, the mean and median 2009 income of people at least 25 years old who had a bachelor's degree but no higher degree were $46,931 and $58,762. Which of these numbers is the mean and which is the median? Explain your reasoning.

2.26 Saving for retirement. Retirement seems a long way off and we need money now, so saving for retirement is hard. Once every three years, the Board of Governors of the Federal Reserve System collects data on household assets and liabilities through the Survey of Consumer Finances (SCF). The most recent such survey was conducted in 2007, and the survey results were released to the public in April 2009. The survey presents data on household ownership of, and balances in, retirement savings accounts. Only 53.6% of households own retirement savings accounts. The mean values per household is $148,579, but the median value is just $45,000. For households in which the head of the household is under 35, 42.6% own retirement accounts, the mean is $25,279, and the median $9600. What explains the differences between the two measures of center, both for all households and for the under-35 age group?