Mean scores on tests that evaluate general knowledge and vocabulary, and mean scores on tests that evaluate memory and information-processing speed are shown in Table 48 for various ages. (The higher the mean score, the better the mental function will be. The mean score for everyone in the study is 0.) Let y be the mean score (in points) on memory and information-processing speed tests for people at age x years.
a. Construct a scatterplot that compares values of x and y.
b. Describe the four characteristics of the association. Compute and interpret r as part of your analysis.
c. Find the linear regression equation.
d. Construct a residual plot. Does it support any of the conclusions you made in part (b)? If yes, which one(s)?
e. Find the coefficient of determination. What does it mean in this situation?