R: Tukey's WSD post-hoc test of means for unequal variance and...

tukeySEM {semTools} | R Documentation

## Tukey's WSD post-hoc test of means for unequal variance and sample size

### Description

This function computes Tukey's WSD post hoc test of means when variances and sample sizes are not equal across groups. It can be used as a post hoc test when comparing latent means in multiple group SEM.

### Usage

    tukeySEM(m1, m2, var1, var2, n1, n2, ng)

### Arguments

`m1` | Mean of group 1.
`m2` | Mean of group 2.
`var1` | Variance of group 1.
`var2` | Variance of group 2.
`n1` | Sample size of group 1.
`n2` | Sample size of group 2.
`ng` | Total number of groups to be compared (i.e., the number of groups compared in the omnibus test).

### Details

After conducting an omnibus test of means across three of more groups, researchers often wish to know which sets of means differ at a particular Type I error rate. Tukey's WSD test holds the error rate stable across multiple comparisons of means. This function implements an adaptation of Tukey's WSD test from Maxwell & Delaney (2004), that allows variances and sample sizes to differ across groups.

### Value

A vector with three elements:

1. `q`: The q statistic

2. `df`: The degrees of freedom for the q statistic

3. `p`: A p value based on the q statistic, df, and the total number of groups to be compared

### Author(s)

Alexander M. Schoemann (East Carolina University; schoemanna@ecu.edu)

### References

Maxwell, S. E., & Delaney, H. D. (2004). Designing experiments and analyzing data: A model comparison perspective (2nd ed.). Mahwah, NJ: Lawrence Erlbaum Associates.

### Examples

    ## For a case where three groups have been compared:
    ## Group 1: mean = 3.91, var = 0.46, n = 246
    ## Group 2: mean = 3.96, var = 0.62, n = 465
    ## Group 3: mean = 2.94, var = 1.07, n = 64

    ## compare group 1 and group 2
    tukeySEM(3.91, 3.96, 0.46, 0.62, 246, 425, 3)

    ## compare group 1 and group 3
    tukeySEM(3.91, 2.94, 0.46, 1.07, 246, 64, 3)

    ## compare group 2 and group 3
    tukeySEM(3.96, 2.94, 0.62, 1.07, 465, 64, 3)

[Package semTools version 0.5-1 Index]