ESS210B
Prof. Jin-Yi Yu
Variance Analysis
qTo calculate the total variance, we
need to know the “mean” è DOF=N-1
qIf we know the mean and the
regression slope (B), then the regression line is set
è
The DOF of the regressed variance is only 1 (the slope).
qThe error variance is determined from
the difference between the total variance (with DOF = N-1) and the
regressed variance (DOF=1) è The DOF of
the error variance = (N-1)-1=N-2.