Table 1 Six methods for defining normal in biomedical science*.
method | Properties of the clinical data, sign, or test |
|---|---|
Gaussian | The statistical distribution of the data is known to be normal in persons without the disease. |
Percentile | Test result lies within a certain percentile of the possible range of results. |
Diagnositic | Research has established the probability that the target disease is present, for a given range of test results. |
Therapeutic | Research has shown that a specific treatment has a known probability of success for a given range of test results. |
Risk factor | Research has shown that presence of a risk factor increases risk of a specified outcome (e.g. morbidity or mortality). |
Culturally desirable | Carries strong socio-political expectations of normal appearance or behaviour. |