com.itemanalysis.psychometrics.irt.estimation

Class RaschScaleQualityStatistics

java.lang.Object

com.itemanalysis.psychometrics.irt.estimation.RaschScaleQualityStatistics

public class RaschScaleQualityStatistics
extends java.lang.Object

Storeless computation of Rasch scale quality statistics such as reliability an separation. Values are computed by incrementally updating each statistic with a new observation. This class is used for both item side quality and person side quality.

Constructor Summary

Constructors

Constructor and Description
RaschScaleQualityStatistics()

Method Summary

Modifier and Type	Method and Description
double	adjustedStandardDeviation() An adjusted standard deviation for computing scale quality statistics.
double	adjustedVariance() An adjusted variance for computing scale quality statistics.
void	increment(double estimate, double stdError) An incremental update to the scale quality statistics.
double	meanSquareError() Mean square error of the estimate.
double	numberOfStrata() Number of distinct strata that are possible with the given estimates.
double	observedStandardDeviation() Observed standard deviation of the estimate.
double	observedVariance() Observed variance of the estimate.
double	reliability() Reliability is the reproduceability of the item or person estimates.
double	rootMeanSquareError() The square root of mean square error.
double	separationIndex() The separation index of scale quality.

Methods inherited from class java.lang.Object

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

Constructor Detail

RaschScaleQualityStatistics

public RaschScaleQualityStatistics()

Method Detail

increment

public void increment(double estimate,
                      double stdError)

An incremental update to the scale quality statistics.

Parameters:

estimate - a person ability or item difficulty estimate.

stdError -

observedVariance

public double observedVariance()

Observed variance of the estimate.

Returns:

observed variance.

observedStandardDeviation

public double observedStandardDeviation()

Observed standard deviation of the estimate.

Returns:

stanmdard deviation.

meanSquareError

public double meanSquareError()

Mean square error of the estimate.

Returns:

mean square error.

rootMeanSquareError

public double rootMeanSquareError()

The square root of mean square error.

Returns:

standard error.

adjustedVariance

public double adjustedVariance()

An adjusted variance for computing scale quality statistics.

Returns:

adjusted variance.

adjustedStandardDeviation

public double adjustedStandardDeviation()

An adjusted standard deviation for computing scale quality statistics.

Returns:

standrd deviation.

separationIndex

public double separationIndex()

The separation index of scale quality.

Returns:

the separation index.

numberOfStrata

public double numberOfStrata()

Number of distinct strata that are possible with the given estimates.

Returns:

number of strata.

reliability

public double reliability()

Reliability is the reproduceability of the item or person estimates.

Returns:

reliability of the estimates.