Potential jurors. Here are descriptive statistics and a scatterplot for the reporting percents in 2003 and 2004 from Table 28.2.
(a) Use the descriptive statistics to compute the least-squares regression line for predicting the reporting percent from the coded reporting date in 2003.
(b) Use the descriptive statistics to compute the least-squares regression line for predicting the reporting percent from the coded reporting date in 2004.
(c) Interpret the value of the slope for each of your estimated models.
(d) Are the two estimated slopes about the same?
(e) Would you be willing to use the multiple regression model with equal slopes to predict the reporting percents in 2003 and 2004? Explain why or why not.
(f) How does the estimated slope in 2003 compare with the estimated slope obtained in Example 28.3 for 1998 and 2000?
(g) Based on the descriptive statistics and scatterplots provided in Exercise 28.3, Example 28.1, and on page 28-11, do you think that the jury commissioner is happy with the modifications he made to improve the reporting percents?
Exercise 28.3:
Potential jurors. On page 28-11 are descriptive statistics and a scatterplot for the reporting percents in 1985 and 1997 from Table 28.2.
(a) Use the descriptive statistics to compute the least-squares regression line for predicting the reporting percent from the coded reporting date in 1985.
(b) Use the descriptive statistics to compute the least-squares regression line for predicting the reporting percent from the coded reporting date in 1997.
(c) Interpret the value of the slope for each of your estimated models.
(d) Are the two estimated slopes about the same?
(e) Would you be willing to use the multiple regression model with equal slopes to predict the reporting percents in 1985 and 1997? Explain why or why not.
Example 28.1:
STATE: Tom Shields, jury commissioner for the Franklin County Municipal Court in Columbus, Ohio, is responsible for making sure that the judges have enough potential jurors to conduct jury trials. Only a small percent of cases go to trial, but potential jurors must be available to serve on short notice. Jury duty for this court is two weeks long, so Tom must bring together a new group of potential jurors twenty-six times a year. Random sampling methods are used to obtain a sample of registered voters in Franklin County every two weeks, and these individuals are sent a summons to appear for jury duty. Not all of the voters who receive a summons actually appear for jury duty. Table 28.1 shows the percent of individuals who reported for jury duty after receiving a summons for two years, 1998 and 2000.1 The reporting dates vary slightly from year to year, so they are coded in order from 1, the first group to report in January, to 26, the last group to report in December. New efforts were made to increase participation rates in 2000. Is there evidence that these efforts were successful?