var.Item: Calculate the variance of an Item
In irt: Item Response Theory and Computerized Adaptive Testing Functions

var,Item-method

R Documentation

Calculate the variance of an Item

Description

var Returns the variance of an item or multiple items with given parameters for a given ability or abilities, i.e. \theta.

Usage

## S4 method for signature 'Item'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature 'Rasch'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature '1PL'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature '2PL'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature '3PL'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature '4PL'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature 'GRM'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature 'PCM'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature 'GPCM'
var(x, y = NULL, na.rm = FALSE, use)

## S4 method for signature 'GPCM2'
var(x, y = NULL, na.rm = FALSE, use)

Arguments

`x`	An `Item-class` or an `Itempool-class` object containing the item parameters.
`y`	A numeric vector containing the ability parameters (i.e. theta).
`na.rm`	Ignored for `var(Item, ...)`
`use`	Ignored for `var(Item, ...)`