# composite_u_scalar: Scalar formula to estimate the u ratio of a composite... In psychmeta: Psychometric Meta-Analysis Toolkit

## Description

This function provides an approximation of the u ratio of a composite variable based on the u ratios of the component variables, the mean restricted intercorrelation among those variables, and the mean unrestricted correlation among those variables. If only one of the mean intercorrelations is known, the other will be estimated using the bivariate indirect range-restriction formula. This tends to compute a conservative estimate of the u ratio associated with a composite.

## Usage

 1 composite_u_scalar(mean_ri = NULL, mean_ra = NULL, mean_u, k_vars) 

## Arguments

 mean_ri The mean range-restricted correlation among variables in the composite. mean_ra The mean unrestricted correlation among variables in the composite. mean_u The mean u ratio of variables in the composite. k_vars The number of variables in the composite.

## Details

This is computed as:

\mjdeqn

u_composite=\sqrt\frac\bar\rho_i\baru^2k(k-1)+k\baru^2\bar\rho_ak(k-1)+ku_composite = sqrt((mean_ri * mean_u^2 * k * (k - 1) + k * mean_u^2) / (mean_ra * k_vars * (k - 1) + k))

where \mjeqnu_compositeu_composite is the composite u ratio, \mjeqn\barumean_u is the mean univariate u ratio, \mjeqn\bar\rho_imean_ri is the mean restricted correlation among variables, \mjeqn\bar\rho_amean_ra is the mean unrestricted correlation among variables, and k is the number of variables in the composite.

## Value

The estimated u ratio of the composite variable.

## Examples

 1 composite_u_scalar(mean_ri = .3, mean_ra = .4, mean_u = .8, k_vars = 2) 

psychmeta documentation built on June 1, 2021, 9:13 a.m.