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' ) 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)
Value
A vector of adjusted sample sizes.
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^2p(1-p)+22p(1-p)var_en_adjusted = ((d^2 * p * (1 - p) + 2) / (2 * p * (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.).
Sage. tools:::Rd_expr_doi("10.4135/9781483398105"). Chapter 7 (Equations 7.23 and 7.23a).