Just guessing on this, but SST (not the transformed, but just ordinary sum of squares total) is the sum of squared deviations from the mean, so I believe that TSST would be the sum of squared deviations from the transformed mean.  Since the intercept is defined by 0= a*Xbar + b, where Xbar is the mean, so would the transformed intercept be defined by 0 = a'X'bar +b' where I defined the primed values as the transformed values, especially the transformed mean.  I would think given what you have that you could plug in the "transformed intercept" and the untransformed intercept, get the difference, add that to the untransformed mean, and then calculate TSST.  AND I will wager a large sum of money that there is probably an easier way. Steve Denham ... View more