Data management/Exploration & description

The box plot produced by Graphics → Boxplot… suggests that the cow with the short lactation, namely Cow 190, is an outlier. We thus delete the record for this cow as its offtake may not be a true reflection of its yield potential.

The skewness of the histogram for lactation offtake indicates that there are also other cows that had somewhat shorter lactation than others. A ranking of cows on the basis of their total lactation offtake might, therefore, tend to favour cows that lactated over longer periods.

 To counteract this we shall attempt to truncate lactations to a fixed period and calculate the total offtake to that point. This is typically done in Europe where lactations of dairy cows are measured to 305 days.