Josephine College, director of the program evaluation unit for the Ohio Department of Higher Education, wants to be able to forecast the percentage of students that will finish high school so that they can plan for any needed expansion in college students. She uses a time series regression with the dependent variable the percentage of persons 25 and older who are high school graduates. The independent variable is a trend variable coded 1 in the year 1991. A regression analysis produces the following results:
 = 61.6 + .42 X r2 = .54 Sy|x = 4.47 sb = .066 n = 24
Interpret the slope, intercept, and coefficient of determination. Test the slope for significance. Predict the percentage of high school graduates in 2015.