trig
posted by jerson on .
for a set of data the line of best fit is given by y=.687x + 3.431 and r^2=.325. what is the correlation efficient

The correlation coefficient (r) is just the square root of r² ... but there are two square roots of r², namely +r and r. However, there's a clue: the line of best fit has a negative slope  so that tells you the sign of r.