The percentages of college freshmen whose average grade in high school was an A are shown in Table 10 for various years.

Let p be the percentage of college freshmen whose average grade in high school was an A at t years since 1970.
a. Construct a scatterplot.
b. Describe the four characteristics of the association. Compute and interpret r as part of your analysis.
c. A model of the situation is p = 0.76t + 18.06. Graph the model on the scatterplot. Does it come close to the data points?
d. Estimate when 44% of all college freshmen earned an average grade of A in high school.
e. Describe at least two possible lurking variables.

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Table 10 College Freshmen Whose Average Grade in High School Was an A Year Percent 1970 1980 1985 1990 1995 2000 2005 2010 19.6 26.6 28.7 29.4 36.1 42.9 46.6 48.4