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Unformatted text preview: Stat 501 Assignment 3 ANSWERS 1. It appears that the right equation for the mean has been used; there’s no curvature apparent in the residual plot. There may be a slight nonconstant variance, but nothing particularly serious. 2. The plots support the assumption that the errors have a normal distribution. The histogram is no perfectly bellshaped, but it is not clearly skewed either. 3. ( i) The plot of the data shows some curvature and also the variance of stopping distance increases as speed increases. (ii) The residual plot shows curvature indicating that the wrong regression equation has been used. There also is evidence of nonconstant variance. (iii) The residual plot for the model with y = square root of distance looks reasonably good. There’s no curvature so the regression equation seems to be appropriate. There is a slight nonconstant variance, but nothing serious. 4. a. 185 180 175 170 165 160 155 150 190 180 170 160 150 Height DesiredHt Scatterplot of DesiredHt vs Height There’s a moderately strong positive association. It looks like a straightline may work as a model. A few There’s a moderately strong positive association....
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This note was uploaded on 03/19/2008 for the course STAT 501 taught by Professor Heckard,robertf during the Fall '07 term at Penn State.
 Fall '07
 HECKARD,ROBERTF
 Variance

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