10.30 Grade inflation. The average undergraduate GPA for American colleges and universities was estimated based on a sample of institutions that published this information.¹³ Here are the data for public schools in that report:

Year	1992	1996	2002	2007
GPA	2.85	2.90	2.97	3.01

Do the following by hand or with a calculator and verify your results with a software package.

(a) Make a scatterplot that shows the increase in GPA over time. Does a linear increase appear reasonable?
(b) Find the equation of the least-squares regression line for predicting GPA from year. Add this line to your scatterplot.
(c) Compute a 95% confidence interval for the slope and summarize what this interval tells you about the increase in GPA over time.