| regression | 1. A return to a former or earlier state. 2. A subsidence of symptoms or of a disease process. 3. <psychiatry> A return to earlier, especially to infantile, patterns of thought or behaviour, a characteristic of many mental disorders also exhibited by normal persons in many situations, for example feelings of helplessness and dependency in a patient with a serious physical illness. Origin: L. Regressio = a return (18 Nov 1997) |
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| regression analysis | Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see linear models) the relationship is constrained to be a straight line and least-squares analysis is used to determine the best fit. In logistic regression (see logistic models) the dependent variable is qualitative rather than continuously variable and likelihood functions are used to find the best relationship. In multiple regression the dependent variable is considered to depend on more than a single independent variable. (12 Dec 1998) |
| regression of the mean | If, for a symmetrical population with a single mode, a measurement, selected because it is extreme, is repeated, on average the second reading will be closer to the mean than the first. (05 Mar 2000) |
| phonaemic regression | A decrease in intelligibility of speech associated with an increase in loudness. (05 Mar 2000) |
| mullerian regression factor | Mullerian duct inhibitory factor, a non-steroidal substance of foetal testicular origin that acts unilaterally to inhibit development of the paramesonephric (mullerian) ducts and acts with testosterone to promote development of the vas deferens and related structures. (05 Mar 2000) |
| corpus luteum regression | Involution and cessation of endocrine function of a corpus luteum. (12 Dec 1998) |
| neoplasm regression, spontaneous | Disappearance of a neoplasm or neoplastic state without the intervention of therapy. (12 Dec 1998) |
| law of regression to mean | In a population mating at random, the progeny of a parent with an extreme value for a measurable phenotype will tend on average to have values nearer the population mean than in the extreme parent. See: law of regression to mean. Synonym: law of regression to mean. (05 Mar 2000) |
| programming, linear | A technique of operations research for solving certain kinds of problems involving many variables where a best value or set of best values is to be found. It is most likely to be feasible when the quantity to be optimised, sometimes called the objective function, can be stated as a mathematical expression in terms of the various activities within the system, and when this expression is simply proportional to the measure of the activities, i.e., is linear, and when all the restrictions are also linear. It is different from computer programming, although problems using linear programming techniques may be programmed on a computer. (12 Dec 1998) |
| non-linear | Not linear. (05 Dec 1998) |
| superficial linear keratitis | Spontaneous, painful keratitis with epithelial erosion and folds in Bowman's membrane. (05 Mar 2000) |
| linear | Pertaining to or resembling a line. Origin: L. Linearis (18 Nov 1997) |
| linear absorption coefficient | That fraction of ionizing radiation absorbed in a unit thickness of a substance or tissue. See: absorption coefficient. (05 Mar 2000) |
| linear acceleration | The rate of change of velocity without a change in direction; e.g., when the speed of an aircraft increases while flying a straight pathway. (05 Mar 2000) |
| linear accelerator | <apparatus> A sophisticated external beam radiotherapy machine which has the capabilities of focussing irradiation (although not very finely). Acronym: LinAC (16 Dec 1997) |