Skip to main content

Table 1 Six methods for defining normal in biomedical science*.

From: Lumbar segmental mobility disorders: comparison of two methods of defining abnormal displacement kinematics in a cohort of patients with non-specific mechanical low back pain

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.
  1. Notes: *as described by Sackett et al (1997) and Smith (2002).