| cohort | <statistics> A cohort is a group of animals of the same species, identified by a common characteristic, which are studied over a period of time as part of a scientific or medical investigation. (09 Oct 1997) |
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| cohort effect | Variation in health status arising from different causal factors to which each birth cohort in a population is exposed as environment and society change. (12 Dec 1998) |
| cohort studies | Studies in which subsets of a defined population are identified. These groups may or may not be exposed to factors hypothesised to influence the probability of the occurrence of a particular disease or other outcome. Cohorts are defined populations which, as a whole, are followed in an attempt to determine distinguishing subgroup characteristics. (12 Dec 1998) |
| cohort study | A study using epidemiological methods, such as a clinical trial, in which a cohort with a particular attribute (e.g., smokers, recipients of a drug) is followed prospectively and compared for some outcome (e.g., disease, cure) with another cohort not possessing the attribute. (05 Mar 2000) |
| angle of incidence | <optics> The angle that a ray entering a refracting medium makes with a line drawn perpendicular to the surface of this medium, the angle that a ray striking a reflecting surface makes with a line perpendicular to this surface. Synonym: incident angle. (05 Mar 2000) |
| plane of incidence | The plane perpendicular to a lens surface that contains the incident light ray. (05 Mar 2000) |
| incidence | 1. An act or the fact or manner of falling upon or affecting. 2. <statistics> Rate, range or amount of occurrence or influence. (18 Nov 1997) |
| incidence density | The person-time incidence rate. (05 Mar 2000) |
| incidence rate | The rate at which new events occur in a population. The numerator is the number of new events occurring in a defined period; the denominator is the population at risk of experiencing the event during this period. (05 Mar 2000) |