correct_glass_bias: Correct for small-sample bias in Glass' \mjseqn\Delta values

Description Usage Arguments Details Value References Examples

View source: R/correct_d.R

Description

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Correct for small-sample bias in Glass' \mjseqn\Delta values.

Usage

1
correct_glass_bias(delta, nc, ne, use_pooled_sd = rep(FALSE, length(delta)))

Arguments

delta

Vector of Glass' \mjseqn\Delta values.

nc

Vector of control-group sample sizes.

ne

Vector of experimental-group sample sizes.

use_pooled_sd

Logical vector determining whether the pooled standard deviation was used (TRUE) or not (FALSE; default).

Details

The bias correction is estimated as:

\mjdeqn\Delta

_c=\Delta_obs\frac\Gamma\left(\fracn_control-12\right)\Gamma\left(\fracn_control-12\right)\Gamma\left(\fracn_control-22\right)delta_c = delta * gamma((nc - 1) / 2) / (sqrt((nc - 1) / 2) * gamma((nc - 2) / 2))

where \mjseqn\Delta is the observed effect size, \mjeqn\Delta_c\Delta_c is the corrected estimate of \mjseqn\Delta, \mjeqnn_controlnc is the control-group sample size, and \mjeqn\Gamma()gamma() is the gamma function.

Value

Vector of d values corrected for small-sample bias.

References

Hedges, L. V. (1981). Distribution theory for Glass’s estimator of effect size and related estimators. Journal of Educational Statistics, 6(2), 107–128. doi: 10.2307/1164588

Examples

1
correct_glass_bias(delta = .3, nc = 30, ne = 30)

Example output

This is psychmeta 0.1.0
Please report any bugs to improve functionality. 

We work hard to produce these open-source tools for the R community - please cite psychmeta when you use it in your research: 
Dahlke, J. A. & Wiernik, B. M. (2017). psychmeta: Psychometric meta-analysis toolkit. R package version 0.1.0
[1] 0.2921625

psychmeta documentation built on June 1, 2021, 9:13 a.m.