From Big Medical Encyclopedia

DECISIVE RULE — the rule of making decision on a condition of a body of interest at incomplete information. In medicine of Genitive find the increasing application in problems of diagnosis and reference of patients to risk groups, especially in connection with a possibility of carrying out difficult calculations on the COMPUTER (see. Diagnosis, cybernetic methods ).

The list of possible conditions of an object is considered in advance known, and the decision is made on the basis of the prior probabilities of states or with use of these observations distorted by hindrances over an object. In nek-ry types of Genitive the cost of observations is considered. Characteristics of Genitive are also the average losses connected with wrong (and sometimes and correct) decisions, and also conditional probabilities of false decisions.

At number of possible conditions of an object more than two decisions belong to multialternative, at two possible states — to two-alternative. The condition of an object, a cut is described by one parameter, call simple, and in other cases — difficult.

Genitive, in to-rykh is supposed use of observations, come down to comparison of the so-called likelihood ratio (LR) with one or several threshold levels. OP is a number, a cut is calculated after the end of observation over object of experience or is consecutive, during experience.

Special type of Genitive is the decisive rule according to Neumann — to Pearson, in Krom one of conditional probabilities of mistakes (e.g., conditional probability to make the decision of Ng when H0 is true), and a threshold of T is set in advance, about the Crimea OP is compared, is defined so that to minimize the second conditional probability (in this case conditional probability of the decision of HQ when Ng is true).

Exist Genitive of consecutive type (PRP), in to-rykh in process of accumulation of results of experience the decision on a condition of an object P0 or the decision on Ng, or the decision on continuation of experience is made. The advantage of PRP is the minimum duration (cost) of experience expected by a set of experiences in comparison with Genitive with the fixed duration of experience at identical conditional probabilities of mistakes.

Many algorithms of a method so-called. recognitions of images (see) in the methodical relation are close to Genitive, however unlike an algorithm of recognition of images at creation of specific Genitive questions of training usually are not considered (see. Algorithm , Algorithm diagnostic , Diagnosis machine ).

Bibliography: Lehman E. L. Check of statistical hypotheses, the lane with English, M., 1979.

A. M. Petrovsky.