adjust_n_d {psychmeta}

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.

Details

The adjusted sample size is computed as:

n_{adjusted}=\frac{d^{2}p(1-p)+2}{2p(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)