We wish to examine the average daily weight gain by calves sired by four bulls selected at random from a population of bulls. Bulls denoted A through D were mated with randomly selected cows. Average daily weight gain was measured for each calf. What is the purpose of this study?
1) To determine the average weight gain of calves sired by bulls A through D
2) To compare the weight gain of calves sired by different bulls
3) To investigate the relationship between bull genetics and calf weight gain
4) To determine the impact of random mating on calf weight gain