Chemistry Reference
In-Depth Information
6
5
4
3
2
1
0
-1
-1
0
1
2
3
4
5
6
2
1
0
-1
-2
-1
0
1
2
3
4
5
6
Predicted Log (EC
50
)
FIGURE 8.3
Good prediction is suggested in this plot of observed Ln (EC
50
) versus the
Ln (EC
50
) predicted for each point that was omitted from the model (top panel). No trends in
prediction quality over the range of predictions were evident in the bottom panel of prediction
residuals versus the predicted ln of the EC
50
.
PROC REG PRESS OUTEST = PSOFT;
MODEL TOTLEC = SOFTCON/AIC BIC;
OUTPUT OUT = LINEAR PREDICTED = PRED RESIDUAL = RES PRESS =
PRES;
RUN;
PROC PRINT;
VAR TOTLEC PRED RES PRES;
RUN;
PROC PRINT DATA = PSOFT;
RUN;
The OUTPUT statement specifies that each prediction residual (PRESS = PRES)
be listed in the output. The PROC REG specifies that the following prediction resid-
ual sum of squares statistic also be generated,
n
∑
ˆ
)
2
PRESS
=
(
y
−
y
.
(8.6)
i
i
i
=
1
This PRESS statistic and the model total sum of squares (
SS
T
) can be combined to
produce a statistic similar to the coefficient of determination (Equation [8.1]) except
