The following data represents the number of days absent and the final grade for a sample of college students in a general education course at a large state university. No. of absences 0 1 2 3 4 5 6 7 8 9
Final Grade 89.2 86.4 83.5 81.1 78.2 73.9 64.3 71.8 65.5 66.2
a) Which variable is the explanatory variable?
b) Draw a scatter plot and describe your scatter plot (Direction, Strength, Form).
c) Compute the correlation coefficient
d) Does a linear relation exist between the number of absences and the final grade? Justify your answer.
e) Write out the least-squares regression line equation.
f) Compute and draw the residual (on your scatter plot) for a student who misses 5 class meetings.
g) Explain the slope in context.
h) Is the y-intercept meaningful in this situation? Explain.
i) Compute and interpret the coefficient of determination.
j) Construct a residual plot to verify the requirements of the least-squares regression model.