Calculates and displays type-II analysis-of-variance tables for model objects produced by aov. This is a vastly reduced version of the Anova function from package car
aovtype2(mod)
| mod | aov model object from base R. |
|---|
An object of class "anova", which usually is printed.
Details about how the function works in order of steps taken. Type-II tests are invariant with respect to (full-rank) contrast coding. Type-II tests are calculated according to the principle of marginality, testing each term after all others, except ignoring the term's higher-order relatives. This definition of Type-II tests corresponds to the tests produced by SAS for analysis-of-variance models, where all of the predictors are factors, but not more generally (i.e., when there are quantitative predictors).
: Fox, J. (2016) Applied Regression Analysis and Generalized Linear Models, Third Edition. Sage.
John Fox jfox@mcmaster.ca; as modified by Chuck Powell
mtcars$cyl <- factor(mtcars$cyl) mtcars$am <- factor(mtcars$am) mod <- aov(hp ~ cyl * am, data = mtcars) aovtype2(mod)#> Anova Table (Type II tests) #> #> Response: hp #> Sum Sq Df F value Pr(>F) #> cyl 102729 2 60.1644 1.759e-10 *** #> am 7318 1 8.5716 0.007009 ** #> cyl:am 12181 2 7.1341 0.003390 ** #> Residuals 22197 26 #> --- #> Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1