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Study questions
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We have assumed that regression lines between weaning
weight and age at weaning are parallel for each year. Fit a statistical model to
include an overall regression line and an interaction with year and comment on
your findings.
- The data analysis has been done on lambs that survived
to weaning. You will note from an earlier table that survival rate was greater
in the Red Maasai than the Dorper lambs. On the basis of an average of 100
Dorper and 100 Red Maasai lambs that might be born in a flock, and assuming the
growth rates and survival rates given in this study, calculate the total weight
of the lambs that reach weaning for each breed. Compare the results with those given for weaning weight in this case
study. Comment.
- A few weights for lambs that were still alive at
weaning were missing in the data sheet at weaning. Is there any way that these
weights might be estimated from other weights recorded for the lambs? If so,
explain how you might do so. Comment on whether this would be necessary for this data set.
- Use the GenStat Spread
 Sheet Title… facility as an alternative method of documenting the data. Comment on the advantages/disadvantages of this method compared with that used in the case study.
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