The National Sheep Improvement Program is a computerized, performance-based program for genetic selection. NSIP is designed to help purebred sheep producers identify the best genetic stock for their breeding programs.

An Expected Progeny Difference (EPD) is an estimate of the genetic merit of an animal for a single trait. Specifically, the EPD of an animal is the expected difference between the performance of that animal's progeny and the average progeny performance of all the animals in the breed, for that trait.