Findings, implications and lessons learned

Regression analysis

• There is a difference in mean milk offtake between cows sampled in Bilisia and Assa.
• Milk offtake declined with age of calf (or stage of lactation) at Bilisa but not Assa.
• Residual patterns in the data suggest that certain observations may have been influential in determining the fitted patterns and that there were others that possibly did not belong to the overall pattern.
• The last point has implications on the suitability of the study design that will be investigated further in the study questions. It illustrates some of the difficulties in interpreting results from small studies.

We have also seen how by switching of the order in which the factor LOCATION is coded, in other words redefining the reference level, we can calculate standard errors for both levels.