adjust_n_d: Adjusted sample size for a non-Cohen _d_ value for use in a...

In psychmeta: Psychometric Meta-Analysis Toolkit

Adjusted sample size for a non-Cohen d value for use in a meta-analysis of Cohen's d values

Description

This function is used to convert a non-Cohen d value (e.g., Glass' Δ) to a Cohen's d value by identifying the sample size of a Cohen's d that has the same standard error as the non-Cohen d. This function permits users to account for the influence of sporadic corrections on the sampling variance of d prior to use in a meta-analysis.

Usage

adjust_n_d(d, var_e, p = NA)

Arguments

d	Vector of non-Cohen d standardized mean differences.
var_e	Vector of error variances of standardized mean differences.
p	Proportion of participants in a study belonging to one of the two groups being contrasted.

Details

The adjusted sample size is computed as:

n_adjusted = ((d^2 * p * (1 - p) + 2) / (2 * p * (1 - p) * var_e))

Value

A vector of adjusted sample sizes.

References

Schmidt, F. L., & Hunter, J. E. (2015). Methods of meta-analysis: Correcting error and bias in research findings (3rd ed.). Sage. doi: 10.4135/9781483398105. Chapter 7 (Equations 7.23 and 7.23a).

Examples

adjust_n_d(d = 1, var_e = .03, p = NA)

psychmeta documentation built on Aug. 26, 2022, 5:14 p.m.