var.Item: Calculate the variance of an Item

In irt: Item Response Theory and Computerized Adaptive Testing Functions

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. θ.

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, ...)

Value

Item variances at given theta will be returned.

Author(s)

Emre Gonulates

irt documentation built on Nov. 10, 2022, 5:50 p.m.