The table shown to the right gives the national average pupil-teacher ratio in public schools over selected years. Year Ratio a. Find the equation for the least squares line. Let x correspond to the number of years since 1990 and let y correspond to the average number of 1990 16.4 pupils per 1 teacher. 1992 16.7 b. Use the answer from part a to predict the pupil-teacher ratio in 2020. Does this seem realistic? 1994 15.9 c. Calculate and interpret the correlation coefficient. 1996 15.2 1998 13.8