Question

5. For a random sample of 50 American cities, the linear correlation coefficient between the number of homocides last year and the number of schools in the city was found to be r = 0.653. a. What does this imply?

b. Does this suggest that building more schools in a city could lead to higher levels of homocides? Why or why not?

c. What is a likely lurking variable?

6. The data below are the first exam scores of 10 randomly selected members of a prior stats class and the number of hours they slept the night before the exam.

Hours x	4	6	5	8	4	5	6	9	7	6
Scores y	70	82	65	90	61	80	86	89	90	70

a. Find the equation of the regression line for the given data. Round the regression line values to the nearest hundredth.

b. What would be the predicted score for a stats student who pulled an all nighter (got 0 hours of sleep) the previous night? Round the predicted score to the nearest whole number.

c. Is this a reasonable question? Explain why or why not.

9. Each year a nationally recognized publication conducts its "Survey of America's Best Graduate and Professional Schools." An academic advisor wants to predict the typical starting salary of a graduate at a top business school using GMAT score of the school as a predictor variable. Total GMAT scores range from 200 to 800. A simple linear regression of SALARY versus GMAT using 25 data points shown below.

Ά0 = -92040 Ά1 = 228 s = 3213 R 2 = 0.66 df = 23 t = 6.67

a) Give a practical interpretation of the estimate of the y-intercept of the least squares line. If none exist explain why.

b) Give a practical interpretation of the slope of the least squares line. If none exists explain why.

c) Give a practical interpretation of R2 = .66

d) Find r

Answer 1