adjust_n_d: 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' \(\Delta\)) 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.

Value

A vector of adjusted sample sizes.

Details

## The adjusted sample size is computed as:
$$n_{adjusted}=\frac{d^{2}p(1-p)+2}{2p(1-p)var_{e}}$$

References

Schmidt, F. L., & Hunter, J. E. (2015).
Methods of meta-analysis: Correcting error and bias in research findings (3rd ed.).
Thousand Oaks, CA: SAGE. https://doi.org/10/b6mg. Chapter 7 (Equations 7.23 and 7.23a).