adjust_n_d {psychmeta} | R Documentation |
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 |
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)