Ron Dirkse pointed out an error in problem 6 of the test I posted the other day. Actually it was correct on the test my students took, but I entered it incorrectly when trying to convert to an ASCII version for posting (nice excuse Al). The first formula below should be y = a + bx, rather than ax + b.
> >6. Your AP STATS formula sheet has the following three formulas which relate >to linear regression. > > y = ax + b, b = r *s(y)/s(x), a = y-mean - b(x-mean) > > Show that the regression line always contains the point (x-mean, y-mean)
Ron asked if I did expected an algebraic solution. Yes - about 80% of the students did it correctly.