13.78 True or false: R and R2 For each of the following statements, indicate whether it is true or false. If false, explain why it is false.

a. R2 is always the same as the square of ordinary correlation computed between the values of the response variable and the values yn predicted by the regression model.

b. The multiple correlation, when taking just two variables into consideration, will be same as the ordinary correlation between them while ignoring the sign.

c. In a simple regression model, R2 is same the square of the ordinary correlation between the response and the independent variable.

d. R2 can decrease with the inclusion of an additional variable in the existing regression model.