Analitica (version 1.8.5)

ScheffeTest: Scheffé Test for Multiple Comparisons

Description

Performs Scheffé's post hoc test after fitting an ANOVA model. This test compares all possible pairs of group means, using a critical value based on the F-distribution.

Usage

ScheffeTest(modelo, alpha = 0.05)

Value

An object of class "scheffe" and "comparaciones", containing:

• Resultados: A data frame of pairwise comparisons with difference, critical value, p-value, and significance code.

• Promedios: A named numeric vector of group means.

• Orden_Medias: A character vector with group names ordered from highest to lowest mean.

• Metodo: A character string indicating the test name ("Scheffe").

Arguments

modelo

An object of class aov or lm representing an ANOVA model.

alpha

Significance level (default is 0.05).

Details

The Scheffé test is a conservative method, making it harder to detect significant differences, but reducing the likelihood of Type I errors (false positives). It is especially appropriate when the comparisons were not pre-planned and the number of contrasts is large.

Assumptions: normally distributed residuals and homogeneity of variances.

Advantages: - Very robust to violations of assumptions. - Suitable for complex comparisons, not just pairwise.

Disadvantages: - Very conservative; reduced power. - Not ideal for detecting small differences.

References

Scheffé, H. (1953). "A method for judging all contrasts in the analysis of variance." Biometrika, 40(1/2), 87–104. <https://doi.org/10.1093/biomet/40.1-2.87>

Examples

data(d_e, package = "Analitica")
mod <- aov(Sueldo_actual ~ as.factor(labor), data = d_e)
resultado <- ScheffeTest(mod)
summary(resultado)
plot(resultado)