Exploration & description

This box plot by age of dam illustrates the association between weaning weight and the age of a lamb's dam. There are more 'outliers' shown in this diagram than the one for genotype. This is probably because the variation among genotypes is not accounted for in this series of boxplots. The plot shows that an offspring's weaning weight appears to increase as a dam increases in age from 2 to 5 years and to decrease from 6 years onwards. We can fit age as a factor with seven levels.