AA Statistics Data Worksheet

Hi 

The attached data set pigs concerns the effect of weaning conditions on the weights of pigs.  Weights were recorded for three litters.  One was weaned early (21 days), another was weaned 28 days (medium), and the last was weaned late (35 days).  The weight at weaning (wwt) and weight at 9 weeks (fwt) are shown.  The goal is to predict the fwt.   It is assumed that wwt might have an effect on fwt.

(a) Fit the appropriate ANCOVA model without interaction and check the assumptoins that you can using the residual plots.  Give the ANOVA table, summary table, and residual plots in what you turn in.  (The handout from April 7 has example code.  You do not need to give the scatter plot with lines for (a) or (b)). 

(b) Fit the appropriate ANCOVA model with the interaction term and check the assumptions that you can using the residual plots.  Give the ANOVA table, summary table, and residual plots in what you turn in.

(c) Select one of (a) and (b) that you think is better.  In a sentence or two, justify your choice.   (It may be that neither is great!)

(d) Use the function ANCOVAplot in the attached file to graph the output of the model you selected in (c)I

(e) In a few sentences summarize what you’ve found out about the problem?  (What was significant? What do the parameter estimates tell you?)I=