# hw3 - STAT 4220 HW3(20 points Due on Thu February 11 1...

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STAT 4220 HW3 (20 points) Due on Thu, February 11 1. Consider the CRD we discussed for estimating how the diets aﬀect the coagulation rates of rabbits. The data are given on the K: drive. (a) (4 point) Use R to analyze the data as a completely randomized design. Write down the ANOVA table. See how I converted y and x into vectors. > data1 = read.table("data.3.1.txt") > data1 = as.matrix(data1) > y = as.vector(data1) > x = rep(1:4,each=4) > g = lm(y~factor(x)) > summary(aov(g)) (b) (2 points) Let us use the following commands now (without “factor”). > g1 = lm(y~x) > summary(aov(g1)) What is the diﬀerence and why is the diﬀerence? Explain clearly. (c) (2 points) Plot the residuals against the factor levels. It should be same as the following plot (note the labeling of the x-axis). > plot(x,g\$res,xaxt="n") > mtext(paste("B"),side=1,at=2) > mtext(paste("C"),side=1,at=3) -4 -2 0 2 4 Plot of residual versus factor levels Diets Residuals B C D A (d) (2 points) Draw the Q-Q plot. (e) (1 point) Look at the ANOVA table in problem 1(a) again. What do

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hw3 - STAT 4220 HW3(20 points Due on Thu February 11 1...

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