1. r describes the clustering of the scatter diagram around the SD line, relative to the SDs

: associated with each one-SD increase in x there is an increase of only r SDs in y, on the average

3. r determines the accuracy of the regression estimates through the formula for r.m.s. error.

4. r tells what proportion of the points on the scatter diagram are highly correlated

Of these four statements,

a. exactly one is true

b. exactly two are true

c. exactly three are true

d. all four are true

e. none are true.