com.itemanalysis.psychometrics.irt.estimation

Class RaschFitStatistics

java.lang.Object

com.itemanalysis.psychometrics.irt.estimation.RaschFitStatistics

public class RaschFitStatistics
extends java.lang.Object

Storeless computation of Rasch item or person INFIT and OUTFIT statistics. Statistics are incrementally updated with each observation and then computed before the result is returned.

Field Summary

Fields

Modifier and Type	Field and Description
double	umsNumeratorSum Value in equation that accumulates by calling increment
double	wmsNumeratorSum Value in equation that accumulates by calling increment
double	WniSum Value in equation that accumulates by calling increment
double	WniZ2niSum Value in equation that accumulates by calling increment
double	Z2niSum Value in equation that accumulates by calling increment

Constructor Summary

Constructors

Constructor and Description
RaschFitStatistics()

Method Summary

Modifier and Type	Method and Description
double	getStandardizedUnweightedMeanSquare() Standardized OUTFIT
double	getStandardizedWeightedMeanSquare() Standardized INFIT
double	getUnweightedMeanSquare() Computes and return the OUTFIT mean square fit statistic.
double	getWeightedMeanSquare() Computes and returns the INFIT mean square fit statistic.
void	increment(ItemResponseModel irm, double theta, byte Xni)
double	kurtosisOfResponse(ItemResponseModel irm, double theta) Kurtosis of response Xni.
double	varianceOfResponse(ItemResponseModel irm, double theta) Variance of response Xni.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

Z2niSum

public double Z2niSum

Value in equation that accumulates by calling increment

WniZ2niSum

public double WniZ2niSum

Value in equation that accumulates by calling increment

WniSum

public double WniSum

Value in equation that accumulates by calling increment

umsNumeratorSum

public double umsNumeratorSum

Value in equation that accumulates by calling increment

wmsNumeratorSum

public double wmsNumeratorSum

Value in equation that accumulates by calling increment

Constructor Detail

RaschFitStatistics

public RaschFitStatistics()

Method Detail

increment

public void increment(ItemResponseModel irm,
                      double theta,
                      byte Xni)

getUnweightedMeanSquare

public double getUnweightedMeanSquare()

Computes and return the OUTFIT mean square fit statistic.

Returns:

OUTFIT mean square fit statistic.

getWeightedMeanSquare

public double getWeightedMeanSquare()

Computes and returns the INFIT mean square fit statistic.

Returns:

INFIT mean square fit statistic.

getStandardizedWeightedMeanSquare

public double getStandardizedWeightedMeanSquare()

Standardized INFIT

Returns:

getStandardizedUnweightedMeanSquare

public double getStandardizedUnweightedMeanSquare()

Standardized OUTFIT

Returns:

varianceOfResponse

public double varianceOfResponse(ItemResponseModel irm,
                                 double theta)

Variance of response Xni. This method is needed for computation of fit statistics. NOTE: This value is the same as item information. Perhaps only for Rasch model??

Parameters:

theta - examinee ability

Returns:

kurtosisOfResponse

public double kurtosisOfResponse(ItemResponseModel irm,
                                 double theta)

Kurtosis of response Xni. This method is needed for computation of fit statistics.

Parameters:

theta -

Returns: