A previously significant variable becomes insignificant when a new independent

# A previously significant variable becomes

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Chap 15-42
. Chap 15-43 Detect Collinearity in PHStat Output for the pie sales example: Since there are only two explanatory variables, only one VIF is reported VIF is < 5 There is no evidence of collinearity between Price and Advertising Regression Analysis Price and all other X Regression Statistics Multiple R 0.030437581 R Square 0.000926446 Adjusted R Square -0.075925366 Standard Error 1.21527235 Observations 15 VIF 1.000927305 Add-Ins/ PHStat / Regression / Multiple Regression … Check the “variance inflationary factor (VIF)” box
. Chap 15-44 Qualitative (Dummy) Variables Categorical explanatory variable (dummy variable) with two or more levels: yes or no, on or off, male or female coded as 0 or 1 Regression intercepts are different if the variable is significant Assumes equal slopes for other variables The number of dummy variables needed is (number of levels – 1)
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