Q-Q plots showing the effect of trypsin treatment on the pI of mitochondria. The sums of squares of the residuals are 0.335, 0.143, and 0.081 respectively for A, B, and C, indicating that trypsin treatment changes the mitochondrial pI distribution. The majority of points in A fall below the line, indicating that the trypsin-treated pI distribution is shifted to lower pI.