Confidence interval: A Good Alternative to Repeatability

Abstract

There is a column labelled "CONF" in your sire summary. This lists a Confidence Interval for each bull's predicted difference for milk (PDM). Anytime we calculate a predicted difference for a bull, we are estimating his true genetic quality to the best of our ability. This Confidence Interval is the range of PDM which probably encompasses the true genetic quality of the bull. The Confidence Interval is directly associated with repeatability as shown in table 1. Any Holstein bull with 70% repeatability has a Confidence Interval of ±254 lbs. of PD milk. This means that a bull such as ABS's Money-Make~ (PDM = 1828) probablyahas a true genetic value between +2082 and +1574 (1828 ± 254).