In animal & plant breeding, truncation selection is a standard method in selective breeding in selecting animals to be bred for the next generation. Animals are ranked by their phenotypic value on some trait such as milk production, and the top X% is reproduced. The effects of truncation selection for a continuous trait can be modeled by the standard breeder's equation by using heritability and Truncated normal distributions; on a binary trait, it can be modeled easily using the liability threshold model and then the breeder's equation. It is considered an easy and efficient method of breeding.
In computer science, truncation selection is a selection method used in genetic algorithms to select potential candidate solutions for recombination modeled after the breeding method.
In truncation selection the candidate solutions are ordered by fitness, and some proportion, p, (e.g. p = 1/2, 1/3, etc.), of the fittest individuals are selected and reproduced 1/p times. Truncation selection is less sophisticated than many other selection methods, and is not often used in practice. It is used in Muhlenbein's Breeder Genetic Algorithm.