verbyla | R Documentation |
This function implements the residual maximum likelihood test of \insertCiteVerbyla93;textualskedastic for testing for heteroskedasticity in a linear regression model.
verbyla(mainlm, auxdesign = NA, statonly = FALSE)
mainlm |
Either an object of |
auxdesign |
A |
statonly |
A logical. If |
Verbyla's Test entails fitting a generalised auxiliary regression model in which the response variable is the vector of standardised squared residuals e_i^2/\hat{ω} from the original OLS model and the design matrix is some function of Z, an n \times q matrix consisting of q exogenous variables, appended to a column of ones. The test statistic is half the residual sum of squares from this generalised auxiliary regression. Under the null hypothesis of homoskedasticity, the distribution of the test statistic is asymptotically chi-squared with q degrees of freedom. The test is right-tailed.
An object of class
"htest"
. If object is
not assigned, its attributes are displayed in the console as a
tibble
using tidy
.
mtcars_lm <- lm(mpg ~ wt + qsec + am, data = mtcars) verbyla(mtcars_lm) verbyla(mtcars_lm, auxdesign = "fitted.values")
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