Optimal risk groups
| Group 1 (Error Rate)g | Group 2 (Error Rate) | Group 3 (Error Rate) | Group 4 (Error Rate) | Odds Ratio 1 (P Value) | Odds Ratio 2 (P Value) | Odds Ratio 3 (P Value) | LRT P Valueh | |
|---|---|---|---|---|---|---|---|---|
| 1 cut pointa | 26 and below (1.59) | 27+ (2.58) | – | – | 1.63 (<.001)d | – | – | <.001 |
| 2 cut pointsb | 19 and below (1.34) | 20–28 (1.88) | 29+ (2.6) | – | 1.40 (.10)e | 1.94 (<.001)e | – | <.001 |
| 3 cut pointsc | 24 and below (1.59) | 25–66 (2.44) | 67–90 (3.03) | 91+ (2.07) | 1.54 (<.001)f | 1.91 (<.001)f | 1.30 (.25)f,i | <.001 |
Note:—LRT indicates likelihood ratio test.
↵a Search done for each shift volume level.
↵b Search done by fours.
↵c Search done by tens.
↵d Interpretation: The odds of containing an error are 63% higher for studies in group 2, compared with studies in group 1.
↵e Interpretation: The odds of containing an error are 40% higher for studies in group 2, compared with studies in group 1; the odds of containing an error are 94% higher for studies in group 3, compared with studies in group 1.
↵f Interpretation: The odds of containing an error are 54% higher for studies in group 2, compared studies in group 1; the odds of containing an error are 91% higher for studies in group 3, compared with studies in group 1; the odds of containing an error are 30% higher for studies in group 4, compared with studies in group 1.
↵g Error rate per 1000 exams.
↵h Optimal cutoff points are defined as the ones with the most significant (likelihood ratio test) split.
↵i Odds ratio 3 decreases, seemingly suggesting that group 4 is safer (than 2); however, this is due to sample size limitations in group 4.