com.itemanalysis.psychometrics.irt.estimation

Class ItemResponseSummary

java.lang.Object

com.itemanalysis.psychometrics.irt.estimation.ItemResponseSummary

public class ItemResponseSummary
extends java.lang.Object

This class is used to count and store item response frequencies for JointMaximumLikelihoodEstimation. It is not called directly. Rather, it is called via JointMaximumLikelihoodEstimation.summarizeData(double).

Field Summary

Fields

Modifier and Type	Field and Description
double	adjustment

Constructor Summary

Constructors

Constructor and Description
ItemResponseSummary(VariableName variableName, byte[] scoreCategories)
ItemResponseSummary(VariableName variableName, double adjustment, byte[] scoreCategories)
ItemResponseSummary(VariableName variableName, java.lang.String groupId, double adjustment, byte[] scoreCategories) Create an item response summary object with information about the variable.

Method Summary

Modifier and Type	Method and Description
void	clearCounts() Resets the item counts to zero.
double	getAdjustment() Gets the extreme score adjustment factor.
java.lang.String	getGroupId() Gets the groupId for this item.
int	getNumberOfCategories() Gets the number of score categories for this item.
int	getPositionInArray() Stores the items position in the array of item response models.
int	getScoreCategoryAt(int index) Gets the score point value for a particular category.
void	increment(byte itemResponse) Count frequency of responses in each score category.
boolean	isExtreme() A boolean method that returns true if the item is an extreme minimum or and extreme maximum.
boolean	isExtremeMaximum() An extreme maximum item score is one in which the raw item score equals the minimum possible raw item score.
boolean	isExtremeMinimum() An extreme minimum item score is one in which the raw item score equals the maximum possible raw item score.
double	maxSip() Maximum possible raw item score
double	minSip() Minimum possible raw item score
boolean	sameItemGroup(ItemResponseSummary itemResponseSummary) Compares this item summary to another one to determine of they belong to the same item group.
void	setPositionInArray(int positionInArray) Stores the item's position in the array of item response models.
double	SijAt(int index) Sij is the frequency of responses in this score category or a higher category.
double	Sip() Returns the raw item score.
double	TijAt(int index) Frequencies for each category are stored in an array.
double	Tip() Total number of exmainees responding to this item.
java.lang.String	toString() A string representation of the frequency counts.

Methods inherited from class java.lang.Object

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

Field Detail

adjustment

public double adjustment

Constructor Detail

ItemResponseSummary

public ItemResponseSummary(VariableName variableName,
                           java.lang.String groupId,
                           double adjustment,
                           byte[] scoreCategories)

Create an item response summary object with information about the variable. The groupId is used to determine whether an item is combined with other items in the group. The group Id may be unique to the item or shared for a set of items.

Parameters:

variableName - name of item.

groupId - a groupId for the item.

adjustment - extreme score adjustment.

scoreCategories - category scoring.

ItemResponseSummary

public ItemResponseSummary(VariableName variableName,
                           double adjustment,
                           byte[] scoreCategories)

ItemResponseSummary

public ItemResponseSummary(VariableName variableName,
                           byte[] scoreCategories)

Method Detail

increment

public void increment(byte itemResponse)

Count frequency of responses in each score category.

Parameters:

itemResponse -

TijAt

public double TijAt(int index)

Frequencies for each category are stored in an array. This method gets the frequency of the score category at this index.

Parameters:

index - position of score category.

Returns:

frequency of examinees in a score category.

Tip

public double Tip()

Total number of exmainees responding to this item.

SijAt

public double SijAt(int index)

Sij is the frequency of responses in this score category or a higher category. This method returns the frequency of the score category at this index of higher.

Parameters:

index - position of response frequency.

Returns:

number of examinees responding in this category or a higher category.

Sip

public double Sip()

Returns the raw item score. This number is part of hte item difficulty update in the Rasch, partial credit, and rating scale model. The adjustment is an extreme score adjustment that prevents infinite estimates.

Returns:

minSip

public double minSip()

Minimum possible raw item score

Returns:

maxSip

public double maxSip()

Maximum possible raw item score

Returns:

getNumberOfCategories

public int getNumberOfCategories()

Gets the number of score categories for this item.

Returns:

number of score categories.

getGroupId

public java.lang.String getGroupId()

Gets the groupId for this item.

Returns:

groupID.

getScoreCategoryAt

public int getScoreCategoryAt(int index)

Gets the score point value for a particular category.

Parameters:

index - array position of the category score.

Returns:

score value for the category.

getPositionInArray

public int getPositionInArray()

Stores the items position in the array of item response models. See JointMaximumLikelihoodEstimation.updateDifficulty(com.itemanalysis.psychometrics.irt.model.ItemResponseModel, com.itemanalysis.psychometrics.irt.estimation.ItemResponseSummary, double)

Returns:

the item summary's position in the array if items.

setPositionInArray

public void setPositionInArray(int positionInArray)

Stores the item's position in the array of item response models. It is set during the data summary steps. See JointMaximumLikelihoodEstimation.initializeCounts()

Parameters:

positionInArray -

getAdjustment

public double getAdjustment()

Gets the extreme score adjustment factor.

Returns:

extreme score adjustment.

sameItemGroup

public boolean sameItemGroup(ItemResponseSummary itemResponseSummary)

Compares this item summary to another one to determine of they belong to the same item group. This is needed to determine if items belong to the same rating scale.

Parameters:

itemResponseSummary -

Returns:

isExtremeMaximum

public boolean isExtremeMaximum()

An extreme maximum item score is one in which the raw item score equals the minimum possible raw item score.

Returns:

true if the item is an extreme maximum. Returns false otherwise.

isExtremeMinimum

public boolean isExtremeMinimum()

An extreme minimum item score is one in which the raw item score equals the maximum possible raw item score.

Returns:

true if an extreme minimum. Return false otherwise.

isExtreme

public boolean isExtreme()

A boolean method that returns true if the item is an extreme minimum or and extreme maximum.

Returns:

true if an extreme item. REturn false otherwise.

clearCounts

public void clearCounts()

Resets the item counts to zero. This is needed during the recursive data summary step in JointMaximumLikelihoodEstimation.summarizeData(double).

toString

public java.lang.String toString()

A string representation of the frequency counts. Used for displaying output.

Overrides:

toString in class java.lang.Object

Returns:

a string of frequency counts.