The researchers studied how sample size and family structure affect the accuracy of estimating heritability using a method called bootstrap. They found that for low heritability, more bootstrap replications were needed for smaller sample sizes. The best family sizes for accurate estimates varied depending on the heritability level. For moderate and high heritability, 200 bootstrap replications were sufficient for all sample sizes. For accurate estimates, the optimal family sizes were 25 sires with 20 progenies per sire for moderate heritability, and 40 sires with 10 progenies per sire for high heritability.