An experiment was conducted to compare the weights of the combs of roosters fed two different vitamin-supplemented diets. Twenty-eight healthy roosters were randomly divided into two groups, with one group receiving diet I and the other receiving diet II. After the study period the comb weight (in milligrams) was recorded for each rooster. The data are:
Diet I 73 130 115 144 127 126 112 76 68 101 126 49 110 123
Diet II 80 72 73 60 55 74 67 89 75 66 93 75 68 76
a) Suppose you wanted to conduct a nonparametric test to compare these data. Using α = .05, complete the following:
H0:
Ha: (two-sided):
Value of test statistic:
p-value:
Conclusion:
b) Suppose the experimenters submitted a scientific paper on their results, and received a number of suggestions from referees. One referee suggests that the underlying distributions are normally distributed, and hence that one should compare the two mean weights. Suppose you investigate comparing means assuming normality. Give the formula for the proper statistic to use, and also the p-value.
Formula for test statistic:
p-value: