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Table 7 Classification results

From: Extraction decision and identification of treatment predictors in Class I malocclusions

Ā 

Treatment

Predicted group membership

Total

Non-extraction

Extraction

Original

Count

Non-extraction

377

20

397

Extraction

67

78

145

%

Non-extraction

95.0

5.0

100.0

Extraction

46.2

53.8

100.0

Cross-validateda

Count

Non-extraction

376

21

397

Extraction

67

78

145

%

Non-extraction

94.7

5.3

100.0

Extraction

46.2

53.8

100.0

  1. aCross-validation is done only for those cases in the analysis. In cross-validation, each case is classified by the functions derived from all cases other than that case; 83.9% of original and 83.8% of cross-validated grouped cases were correctly classified. The proportional by chance accuracy rate was computed by squaring and summing the proportion of cases in each group from the table of prior probabilities for groups (0.732ā€‰+ā€‰0.272ā€‰=ā€‰0.607). A 25% increase over this would require that our cross-validated accuracy be 75.8% (1.25ā€‰Ć—ā€‰60.7Ā %ā€‰=ā€‰75.8%). The cross-validated accuracy rate computed by SPSS was 83.8% which was greater than the proportional by chance accuracy criteria of 75.8%.