Table 1 Adjusted TRISS misclassification rate and adjusted w-statistic
TRISS Method | deaths Od | survivors Os | Expected: |
|---|---|---|---|
Positive (P(s) < 50%) | TP | FP | Ed = TP+FP |
a | b | Ed = a+b | |
EOd | Us | Ed = Us+ EOd | |
Negative (P(s) > 50%) | FN | TN | Es = FN+TN |
c = c1+c2 | d | Es = c+d | |
c1 = Pd; | EOs | Es = Ud+EOs | |
c2 = nonPd | |||
Ud | |||
Observed: | Od = TP+FN | Os = FP+TN | N = Ed+Es |
Od = a+c | Os = b+d | N = a+b+c+d | |
Od = EOd+Ud | Os = Us+EOs | N = Od+Os | |
Misclassification rate = (FP + FN)/N = (b + c)/N = (Us + Ud)/N | |||
Adjusted misclassification rate | = (FP+FN-Pd)/N | ||
= (b +c -Pd)/N | |||
= Us + Ud - Pd/N | |||
W statistic | = (FP+TN) - (FN+TN)/N = (FP - FN)/N | ||
= (b+d) - (c+d)/N = (b-c)/N | |||
= (Os - Es)/N | |||
= (Us+EOs) - (Ud + EOs)/N = (Us - Ud)/N | |||
Adjusted W statistic | = [FP-(FN-nonPd)/N = (FP- Pd)/N | ||
= [b - (c - nonPd)]/N = (b - Pd)/N | |||
(c = c1+ c2; Pd = c - nonPd) | |||
= (Us - Pd)/N | |||
= [Os- (Es- nonPd)]/N | |||