# IECV: IECV In BifactorIndicesCalculator: Bifactor Indices Calculator

## Description

Computes an ECV index for each item which can be interpreted as the proportion of common variance of that item due to the general factor. Stucky and Edelen (2015, p. 201) define I-ECV, which is also computed in the Excel version of the bifactor indices calculator (Dueber, 2017).

## Usage

 `1` ```IECV(Lambda) ```

## Arguments

 `Lambda` is a matrix of factor loadings. Be sure that all factors have the same variance before calling this function.

## Details

`IECV` is called by `bifactorIndices` and the various convenience functions for exploratory models and/or Mplus output, which are the only functions in this package intended for casual users.

## Value

A vector of item ECVs

## References

Dueber, D. M. (2017). Bifactor Indices Calculator: A Microsoft Excel-based tool to calculate various indices relevant to bifactor CFA models. doi: 10.13023/edp.tool.01

Stucky, B. D., & Edelen, M. O. (2015). Using hierarchical IRT models to create unidimensional measures from multidimensional data. In S. P. Reise & D. A. Revicki (Eds.), Handbook of item response theory modeling: Applications to typical performance assessment (pp.183-206). New York: Routledge.

`ECV_SS`, `ECV_SG`, `ECV_GS`, `bifactorIndices`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15``` ```Lambda <- matrix(c(.82, .10, 0, 0, .77, .35, 0, 0, .79, .32, 0, 0, .66, .39, 0, 0, .51, 0, .71, 0, .56, 0, .43, 0, .68, 0, .13, 0, .60, 0, .50, 0, .83, 0, 0, .47, .60, 0, 0, .27, .78, 0, 0, .28, .55, 0, 0, .75), ncol = 4, byrow = TRUE) colnames(Lambda) <- c("General", "SF1", "SF2", "SF3") IECV(Lambda) ```