“…Many investigators found that this estimator is optimistically biased for estimating the actual error rate, particularly when the training samples are small (see for example, Dunn and Varady (1966), and Hills (1966)). The other parametric estimators denoted by DS, O, OS, L, and M are modifications (improvements) of the D-estimator with various bias reduction terms, proposed and compared by Okamoto (1963), Lachenbruch (1968), Lachenbruch and Mickey (1968), McLachlan (1974a), Page (1985), Ganeshanandam and Krzanowski (1990), and some others. Some authors also proposed smoothed estimators as bias corrections to D and DS estimators (see Glick (1978), Snapinn (1983), Snapinn and Knoke (1985)).…”