zv.test {vartest}

Z Variance Test

Description

zv.test performs Z variance homogeneity test.

Usage

zv.test(formula, data, alpha = 0.05, na.rm = TRUE, verbose = TRUE)

Arguments

formula

a formula of the form lhs ~ rhs where lhs gives the sample values and rhs the corresponding groups.

data

a tibble or data frame containing the variables in formula.

alpha

the level of significance to assess variance homogeneity. Default is set to alpha = 0.05.

na.rm

a logical value indicating whether NA values should be stripped before the computation proceeds.

verbose

a logical for printing output to R console.

Value

A list containing the following components:

statistic

the corresponding test statistic.

parameter

the parameter(s) of the approximate F distribution of the test statistic.

p.value

the p-value of the test.

method

the character string "Z Variance Test".

data

a data frame containing the variables in which NA values (if exist) are removed.

formula

a formula of the form lhs ~ rhs where lhs gives the sample values and rhs the corresponding groups.

Author(s)

Gozde Cosar and Osman Dag

References

Gorbunova, A.A., Lemeshko, B.Y. (2012). Application of Parametric Homogeneity of Variances Tests under Violation of Classical Assumption. 2nd Stochastic Modeling Techniques and Data Analysis International Conference, 5:8, 253-260.

Wang, Y., Gil, P.R., Chen, Y.H., Kromrey, J.D., Kim, E.S., Pham, T., Nguyen, D., Romano, J.L. (2017). Comparing the Performance of Approaches for Testing the Homogeneity of Variance Assumption in One-Factor Anova Models. Educational and Psychological Measurement, 77:2, 305-329.

Overall, J.E., Woodward, J.A. (1974). A Simple Test for Heterogeneity of Variance in Complex Factorial Designs. Psychometrika, 39:3, 311-318.

Examples

library(vartest)

zv.test(Sepal.Length ~ Species, data = iris)