Symbol: m. The expectation that over a series of observations a certain kind of observation will occur regularly and form a given proportion of the total number of observations. For example, if a plant heterozygous for height, Tt, is selfed, the probability of finding the double recessive, tt, in the progeny is 1/4. The greater the number of progeny, the more likely it is that the actual number of double recessives will approach 25%. See also

chi-squared test.