games.howell: Games-Howell Post-Hoc Test

In visStatistics: Automated Selection and Visualisation of Statistical Hypothesis Tests

Games-Howell Post-Hoc Test

Description

Performs pairwise comparisons using the Games-Howell test, which does not assume equal variances or equal sample sizes. This is the appropriate post-hoc test to use after a significant Welch's ANOVA.

Usage

games.howell(samples, groups, conf.level = 0.95)

Arguments

samples	Numeric vector; the dependent variable.
groups	Factor or vector; the grouping variable.
conf.level	Numeric; confidence level for confidence intervals (default: 0.95).

Details

The Games-Howell test uses the Welch-Satterthwaite approximation for degrees of freedom and does not pool variances. P-values are adjusted using the Holm method to control family-wise error rate.

Value

A data frame with columns:

group1

First group in comparison

group2

Second group in comparison

mean_diff

Difference in means (group1 - group2)

se

Standard error of the difference

t

t-statistic

df

Degrees of freedom (Welch-Satterthwaite)

p_value

Unadjusted p-value

p_adj

Holm-adjusted p-value for multiple comparisons

ci_lower

Lower bound of confidence interval

ci_upper

Upper bound of confidence interval

significant

Logical; TRUE if p_adj < (1 - conf.level)

Examples

# Convert dose to factor
ToothGrowth$dose <- as.factor(ToothGrowth$dose)

# Perform Games-Howell test
result <- games.howell(ToothGrowth$len, ToothGrowth$dose)
print(result)

visStatistics documentation built on May 13, 2026, 1:08 a.m.