| odds ratio | <epidemiology> A comparison of the presence of a risk factor for disease in a sample of diseased subjects and non diseased controls. The number of people with disease who were exposed to a risk factor ( I.e. ) over those with disease who were not exposed ( Io ) divided by those without disease who were exposed ( Ne ) over those without who were not exposed ( No ). Thus OR=(I.e./Io)/(Ne/No)= I.e. No / Io Ne. This measure should be used for case control studies where we retrospectively look at risks in those with and without disease. Also known as exposure odds ratio. (05 Dec 1998) |
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| therapeutic ratio | The ratio of the maximally tolerated dose of a drug to the minimal curative or effective dose; LD50 divided by ED50. (05 Mar 2000) |
| tritium-breeding ratio | <radiobiology> The amount of tritium generated by the breeding blanket of a D-T fusion reactor, divided by the amount of tritium burned in the reactor. A tritium breeding ration greater than unity is necessary for self-sufficient fueling. (09 Oct 1997) |
| turn down ratio | The lowest load at which a boiler will operate efficiently as compared to the boiler's maximum design load. (05 Dec 1998) |
| exposure odds ratio | <epidemiology> See Odds ratio. (05 Dec 1998) |
| extraction ratio | The fraction of a substance removed from the blood flowing through the kidney; it is calculated from the formula (A -V)/A, where A and V, respectively, are the concentrations of the substance in arterial and renal venous plasma. (05 Mar 2000) |
| K:A ratio | <abbreviation> Ketogenic-antiketogenic ratio. (05 Mar 2000) |
| ketogenic-antiketogenic ratio | The proportion between substances that form ketones in the body and those that form d-glucose. (05 Mar 2000) |
| zeta sedimentation ratio | The ratio of the zetacrit to the haematocrit, normally 0.41 to 0.54 (41 to 54%); it is a sensitive indicator of the erythrocyte sedimentation rate (ESR) and, unlike the latter, is unaffected by anaemia, which tends to elevate the ESR. (05 Mar 2000) |
| fertility ratio | A measure of the fertility of a population based on the female population in the child-bearing age-group, defined as ages 15-49 years. (05 Mar 2000) |
| flux ratio | The ratio of the two unidirectional fluxes through a particular boundary layer or membrane. (05 Mar 2000) |
| lecithin/sphingomyelin ratio | A ratio used to determine foetal pulmonary maturity, found by testing the amniotic fluid; when the lungs are mature, lecithin exceeds sphingomyelin by 2 to 1. (05 Mar 2000) |
| functional terminal innervation ratio | The number of muscle fibres divided by the number of axons that innervate them. (05 Mar 2000) |
| low aspect ratio | <physics> An aspect ratio for a torus that is small (minor radius is almost as big as major radius). There are many fusion devices which are designed to have a low aspect ratio. Such devices look more like tractor tires than bicycle tires, as toruses go. There are reasons to believe that low aspect ratio devices will offer some advantages for a fusion reactor. Usually, ease of theoretical and/or numerical analysis is not one of these advantages. (16 Mar 1998) |