Perform Spread-Level test

Tests the slope of log(|residuals|) on log(fitted).

Usage

performSpreadLevelTest(model)

Details

A slope near 0 indicates constant variance. A significant slope suggests a power transformation may stabilize the spread.

Arguments

model

an object of class lm.

Value

An object of class htest.

References

Cleveland, W. S. (1979). Robust locally weighted regression and smoothing scatterplots. Journal of the American Statistical Association, 74(368), 829–836.

Examples

 data(mtcars)
 m <- lm(mpg ~ wt + qsec, data = mtcars)
 performSpreadLevelTest(m)
#> 
#> 	Spread-Level test
#> 
#> data:  mpg ~ wt + qsec
#> t = 0.43832, = 30, p-value = 0.6643
#>