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--- r:dummy_variables_with_significant_interaction [2023/06/05 21:58] – [Regression with a continous + a categorical variables: ANCOVA] hkimscil
+++ r:dummy_variables_with_significant_interaction [2023/06/05 22:01] (current) – [Regression with a continous + a categorical variables: ANCOVA] hkimscil
@@ Line 207: / Line 207: @@
     * y hat ~ 77.3 + .00006*cost
+<code>
+> summary(mod2<-lm(salary~cost * location))
+Call:
+lm(formula = salary ~ cost * location)
+Residuals:
+     Min       1Q   Median       3Q      Max
+-17.1126  -5.6241  -0.8152   2.6401  28.4861
+Coefficients:
+                  Estimate Std. Error t value Pr(>|t|)
+(Intercept)      8.863e+01  4.995e+00  17.744   <2e-16 ***
+cost             5.480e-05  3.211e-05   1.707   0.0919 .
+locationMW      -5.526e+00  7.213e+00  -0.766   0.4460
+locationNE      -2.866e+00  7.383e+00  -0.388   0.6989
+locationW       -1.876e+00  6.509e+00  -0.288   0.7740
+cost:locationMW  1.885e-05  4.681e-05   0.403   0.6882
+cost:locationNE  7.480e-05  4.533e-05   1.650   0.1030
+cost:locationW  -7.815e-05  4.665e-05  -1.675   0.0980 .
+---
+Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
+Residual standard error: 7.644 on 77 degrees of freedom
+Multiple R-squared:  0.6241,	Adjusted R-squared:  0.5899
+F-statistic: 18.26 on 7 and 77 DF,  p-value: 4.313e-14
+> anova(mod2)
+Analysis of Variance Table
+Response: salary
+              Df Sum Sq Mean Sq F value    Pr(>F)
+cost           1 2757.0 2756.97  47.183 1.470e-09 ***
+location       3 4071.8 1357.26  23.228 8.276e-11 ***
+cost:location  3  641.6  213.86   3.660   0.01596 *
+Residuals     77 4499.2   58.43
+---
+Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
+>
+</code>