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

 composite_u_scalar R Documentation

## Scalar formula to estimate the u ratio of a composite variable

### 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

```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:

u_composite = sqrt((mean_ri * mean_u^2 * k * (k - 1) + k * mean_u^2) / (mean_ra * k_vars * (k - 1) + k))

where u_composite is the composite u ratio, mean_u is the mean univariate u ratio, mean_ri is the mean restricted correlation among variables, mean_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

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

psychmeta documentation built on Aug. 26, 2022, 5:14 p.m.