Comment: One row per kind of probability distribution. This table establishes a controlled vocabulary for probability distributions.
code character(1) A unique single character code for the probability type. This code identifies the row within the database.
description text A unique description of the kind of probability distribution.
symmetrical boolean TRUE when the related data-endpoints must be "symmetrical" about the distribution's most likely value, in the same way that the endpoints of a normal distribution are equidistant from the mean, median, and mode. FALSE when the related data need not be. In effect, denotes whether the probability distribution is a normal distribution. When a PROBABILITY_TYPE row is related to data consisting of a value, a minimum, and a maximum (as it is with BIOGRAPHY's BirthDate, BDMin, and BDMax columns) symmetry requires that the value be midway between the minimum and the maximum. Because some intervals are measured in discrete time units (i.e. days) the midpoint is defined to be either one of the 2 midpoint dates when there are an even number of days in the min-to-max interval. The value of this column cannot be changed.