# hw3sol - STAT 4220 HW3 Solution 1 Problem 1 (a) The ANOVA...

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STAT 4220 HW3 Solution 1 Problem 1 (a) The ANOVA table is given below: Degrees of Sum of Mean F p -value Source Freedom Squares Squares Treatment 3 191.5 63.833 9.1737 0.001976 Residual 12 83.5 6.958 Total 15 275 (b) The difference is that the “factor” command treats each distinct value of the predictor as a separate category requiring its own parameter to be estimated. So the model is then of the form y i j = η + τ i + ε i j i , j = 1 ... 4. This model requires that (Number of levels) - 1 = 4 - 1 = 3 degrees of freedom be used estimating the effect of each treatment level. When “factor” is omitted, R then treats this is a simple linear regression model, where each value is just an observation from a continuous predictor. That is, the model is given by y i j = β 0 + β 1 x i + ε i j . In this case, the model requires only (Number of unknown parameters) - 1 = 2 - 1 = 1 degree of freedom for estimating the predictor effect. (c) The Residual vs. Factor level plot is generated by plot(x,g\$res,xaxt="n",xlab= "Diets", ylab= "Residuals",

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## This note was uploaded on 06/06/2011 for the course STAT 4220 taught by Professor Smith during the Spring '08 term at University of Georgia Athens.

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hw3sol - STAT 4220 HW3 Solution 1 Problem 1 (a) The ANOVA...

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