Exploration & description

By restricting the data to 1991 and then fitting a regression line Stats Regression Analysis Linear Models... and completing the dialog box, a regression analysis of weaning weight on weaning age can be obtained. By clicking Further Output, then, clicking Fitted Model in the next dialog box, the scatter plot plus the fitted regression line, as shown for weaning weight versus age at weaning is produced.

Lambs were born over a short period spanning a few weeks but were all weaned together on the same day. There is a general pattern indicating a linear relationship of weaning weight with age.