Table 2 Seven examples of the same test matrix affected by bias of increasing magnitude
From: The test characteristics of a biased or ignorant diagnostician
Bias | Test matrix | Biased test matrix | p and PPV of diagnosis (%) | p and PPV of alternative diagnosis (%) | |||||
|---|---|---|---|---|---|---|---|---|---|
Dx+ (%) | Dx− (%) | Dx+ (%) | Dx− (%) | Dx+ (%) | Dx− (%) | ||||
1st Example | |||||||||
T+ | 100 | 0 | 80 | 10 | 80 | 10 | p | 20 | 80 |
T− | 0 | 100 | 20 | 90 | 20 | 90 | PPV | 67 | 33 |
2nd Example | |||||||||
T+ | 80 | 20 | 80 | 10 | 68 | 26 | p | 20 | 80 |
T− | 20 | 80 | 20 | 90 | 32 | 74 | PPV | 40 | 60 |
3rd Example | |||||||||
T+ | 60 | 40 | 80 | 10 | 56 | 42 | p | 20 | 80 |
T− | 40 | 60 | 20 | 90 | 44 | 58 | PPV | 25 | 75 |
4th Example | |||||||||
T+ | 50 | 50 | 80 | 10 | 50 | 50 | p | 20 | 80 |
T− | 50 | 50 | 20 | 90 | 50 | 50 | PPV | 20 | 80 |
5th Example | |||||||||
T+ | 40 | 60 | 80 | 10 | 44 | 58 | p | 20 | 80 |
T− | 60 | 40 | 20 | 90 | 56 | 42 | PPV | 16 | 84 |
6th Example | |||||||||
T+ | 20 | 80 | 80 | 10 | 32 | 74 | p | 20 | 80 |
T− | 80 | 20 | 20 | 90 | 68 | 26 | PPV | 10 | 90 |
7th Example | |||||||||
T+ | 0 | 100 | 80 | 10 | 20 | 90 | p | 20 | 80 |
T− | 100 | 0 | 20 | 90 | 80 | 10 | PPV | 5 | 95 |