
Bibliography:  Cronbach, L. J. (1951), Coefficient alpha and the internal structure of tests, Psychometrika, 16(3), 297334. 
Cohen, L., Manion, L. & Morrison, K, A. (2008), Research Methods in Education, 6th Edition, Routledge, London & New York, Chapter Six, Validity and reliability, pp 132164.  
Allen, K., ReedRhoads, T., Terry, R. A., Murphy, T. J. & Stone, A. D. (2008), Coefficient Alpha: An Engineer's Interpretation of Test Reliability, Journal of Engineering Education, 97(1), 8794. 
Constructor  public Cronbach()  
Enter the data  Read title, item names and responses from text file 
Enter responses as rows per person 
public void readScoresAsRowPerPersonA() 
public void readScoresAsRowPerPersonA(String filename)  
public void readScoresAsRowPerPersonB()  
public void readScoresAsRowPerPersonB(String filename)  
public void readScoresAsRowPerPersonC()  
public void readScoresAsRowPerPersonC(String filename)  
public void readScoresAsRowPerPersonD()  
public void readScoresAsRowPerPersonD(String filename)  
Enter responses as rows per item 
public void readScoresAsRowPerItemA()  
public void readScoresAsRowPerItemA(Stringfilename)  
public void readScoresAsRowPerItemB()  
public void readScoresAsRowPerItemB(Stringfilename)  
public void readScoresAsRowPerItemC()  
public void readScoresAsRowPerItemC(Stringfilename)  
public void readScoresAsRowPerItemD()  
public void readScoresAsRowPerItemD(Stringfilename)  
Enter data via program arrays and Strings 
Enter responses as rows per person 
public void enterScoresAsRowPerPerson(String[][] responses)  
public void enterScoresAsRowPerPerson(double[][] responses)  
public void enterScoresAsRowPerPerson(float[][] responses)  
public void enterScoresAsRowPerPerson(int[][] responses)  
public void enterScoresAsRowPerPerson(char[][] responses)  
public void enterScoresAsRowPerPerson(boolean[][] responses)  
public void enterScoresAsRowPerPerson(Matrix responses)  
Enter responses as rows per item 
public void enterScoresAsRowPerItem(String[][] responses)  
public void enterScoresAsRowPerItem(double[][] responses)  
public void enterScoresAsRowPerItem(float[][] responses)  
public void enterScoresAsRowPerItem(int[][] responses)  
public void enterScoresAsRowPerItem(char[][] responses)  
public void enterScoresAsRowPerItem(boolean[][] responses)  
public void enterScoresAsRowPerItem(Matrix responses)  
Enter title  public void enterTitle(String title)  
Enter item names  public void enterItemNames(String[] itemNames)  
Additional data entry options  Suspend reading letters as numerals  public void suspendLetterToNumeral()  
public void letterToNumeral()  
Dichotomous data pairs  Reset numerical representation  public void resetDichotomousYesTrue(double newYesTrue)  
public void resetDichotomousNoFalse(double newNoFalse)  
Get numerical representation  public double getDichotomousYesTrue()  
public double getDichotomousNoFalse()  
Additional dichotomous data pairs  public void additionalDichotomousPairs(String falseSign, String trueSign)  
Missing response ('no response') handling 
Deletions  Persons  public void setPersonDeletionPercentage(double percentage) 
Items  public void setItemDeletionPercentage(double percentage)  
Replacements  public void setMissingDataOption(int option)  
Set the denominator (variance, standard deviation etc.)  Set to n  public void setDenominatortoN()  
Set to n1  public void setDenominatortoNminusOne()  
Cronbachs's alpha consistency coefficient 
Raw data alpha  public void rawAlpha()  
Standardized data alpha  public void standardizedAlpha()  
Full analysis  Perform and output a full analysis  public void analysis()  
public void analysis(String filename)  
Set output file type  public void setOutputFileType(int option)  
Set incremented numbering of the output file  public void setFileNumbering()  
Remove incremented numbering of the output file  public void removeFileNumbering()  
Set output precision  public void numberOfDecimalPlaces(int trunc)  
public void numberOfDecimalPlaces(int trunc)  
Scatter plots  Plot of item  item responses  raw data  public void rawItemItemPlot(String itemName1, String itemName2) 
public void rawItemItemPlot(int itemIndex1, int itemIndex2)  
standardized data  public void standardizedItemItemPlot(String itemName1, String itemName2)  
public void standardizedItemItemPlot(int itemIndex1, int itemIndex2)  
Plot of item  mean of items responses  raw data  public void rawItemMeansPlot(String itemName)  
public void rawItemMeansPlot(int itemIndex)  
standardized data  public void standardizedItemMeansPlot(String itemName)  
public void standardizedItemMeansPlot(int itemIndex)  
Delete an item  delete by name  public double[][] deleteItem(String itemName)  
delete by index  public double[][] deleteItem(int itemIndex)  
Correlation coefficients  Between all items  Correlation coefficient matrix  public double[][] rawCorrelationCoefficients() 
public double[][] standardizedCorrelationCoefficients()  
Average correlation coefficient  public double rawAverageCorrelationCoefficients()  
public double standardizedAverageCorrelationCoefficients()  
Average correlation coefficient including item totals 
public double rawAverageCorrelationCoefficientsWithTotals()  
public double standardizedAverageCorrelationCoefficientsWithTotals()  
Standard deviation of the correlation coefficients  public double rawStandardDeviationCorrelationCoefficients()  
public double standardizedStandardDeviationCorrelationCoefficients()  
Standard deviation of the correlation coefficient including item totals 
public double rawStandardDeviationCorrelationCoefficientsWithTotals()  
public double standardizedStandardDeviationCorrelationCoefficientsWithTotals()  
Between pairs  Itemitem pair  public double rawCorrelationCoefficient(String itemName1, String itemName2)  
public double rawCorrelationCoefficient(int itemIndex1, int itemIndex2)  
public double standardizedCorrelationCoefficient(String itemName1, String itemName2)  
public double standardizedCorrelationCoefficient(int itemIndex1, int itemIndex2)  
Item(totals of the items) pair  public double rawCorrelationCoefficient(String itemName)  
public double rawCorrelationCoefficient(int itemIndex)  
public double standardizedCorrelationCoefficient(String itemName)  
public double standardizedCorrelationCoefficient(int itemIndex)  
Covariances  Between all items  Covariance matrix/td>  public double[][] rawCovariances() 
public double[][] standardizedCovariances()  
Between pairs  Itemitem pair  public double rawCovariance(String itemName1, String itemName2)  
public double rawCovariance(int itemIndex1, int itemIndex2)  
public double standardizedCovariance(String itemName1, String itemName2)  
public double standardizedCovariance(int itemIndex1, int itemIndex2)  
Item(totals of the items) pair  public double rawCovariance(String itemName)  
public double rawCovariance(int itemIndex)  
public double standardizedCovariance(String itemName)  
public double standardizedCovariance(int itemIndex)  
Item means  Mean values of all items  Raw data  public double[] rawItemMeans() 
Standardized data  public double[] standardizedItemMeans()  
Mean value of an individual item  Raw data  public double rawItemMean(int index)  
public double rawItemMean(String name)  
Standardized data  public double standardizedItemMean(int index)  
public double standardizedItemMean(String name)  
Mean value of all item means  Raw data  public double rawMeanOfItemMeans()  
Standardized data  public double standardizedMeanOfItemMeans()  
Standard deviation of all item means  Raw data  public double rawStandardDeviationOfItemMeans()  
Standardized data  public double standardizedStandardDeviationOfItemMeans()  
Variance of all item means  Raw data  public double rawVarianceOfItemMeans()  
Standardized data  public double standardizedVarianceOfItemMeans()  
Maximum of all item means  Raw data  public double rawMaximumOfItemMeans()  
Standardized data  public double standardizedMaximumOfItemMeans()  
Minimum of all item means  Raw data  public double rawMinimumOfItemMeans()  
Standardized data  public double standardizedMinimumOfItemMeans()  
Range of all item means  Raw data  public double rawRangeOfItemMeans()  
Standardized data  public double standardizedRangeOfItemMeans()  
Item standard deviations  Standard deviations of all items  Raw data  public double[] rawItemStandardDeviations() 
Standardized data  public double[] standardizedItemStandardDeviations()  
Standard deviation value of an individual item  Raw data  public double rawItemStandardDeviation(int index)  
public double rawItemStandardDeviation(String name)  
Standardized data  public double standardizedItemStandardDeviation(int index)  
public double standardizedItemStandardDeviation(String name)  
Mean value of all item standard deviations  Raw data  public double rawMeanOfItemStandardDeviations()  
Standardized data  public double standardizedMeanOfItemStandardDeviations()  
Standard deviation of all item standard deviations  Raw data  public double rawStandardDeviationOfItemStandardDeviations()  
Standardized data  public double standardizedStandardDeviationOfItemStandardDeviations()  
Variance of all item standard deviations  Raw data  public double rawVarianceOfItemStandardDeviations()  
Standardized data  public double standardizedVarianceOfItemStandardDeviations()  
Maximum of all item standard deviations  Raw data  public double rawMaximumOfItemStandardDeviations()  
Standardized data  public double standardizedMaximumOfItemStandardDeviations()  
Minimum of all item standard deviations  Raw data  public double rawMinimumOfItemStandardDeviations()  
Standardized data  public double standardizedMinimumOfItemStandardDeviations()  
Range of all item standard deviations  Raw data  public double rawRangeOfItemStandardDeviations()  
Standardized data  public double standardizedRangeOfItemStandardDeviations()  
Item variances  Variances of all items  Raw data  public double[] rawItemVariances() 
Standardized data  public double[] standardizedItemVariances()  
Variance of an individual item  Raw data  public double rawItemVariance(int index)  
public double rawItemVariance(String name)  
Standardized data  public double standardizedItemVariance(int index)  
public double standardizedItemVariance(String name)  
Mean value of all item variances  Raw data  public double rawMeanOfItemVariances()  
Standardized data  public double standardizedMeanOfItemVariances()  
Standard deviation of all item variances  Raw data  public double rawVarianceOfItemVariances()  
Standardized data  public double standardizedVarianceOfItemVariances()  
Variance of all item variances  Raw data  public double rawVarianceOfItemVariances()  
Standardized data  public double standardizedVarianceOfItemVariances()  
Maximum of all item variances  Raw data  public double rawMaximumOfItemVariances()  
Standardized data  public double standardizedMaximumOfItemVariances()  
Minimum of all item variances  Raw data  public double rawMinimumOfItemVariances()  
Standardized data  public double standardizedMinimumOfItemVariances()  
Range of all item variances  Raw data  public double rawRangeOfItemVariances()  
Standardized data  public double standardizedRangeOfItemVariances()  
Item maxima  Maxima of all items  Raw data  public double[] rawItemMaxima() 
Standardized data  public double[] standardizedItemMaxima()  
Maximum of an individual item  Raw data  public double rawItemMaximum(int index)  
public double rawItemMaximum(String name)  
Standardized data  public double standardizedItemMaximum(int index)  
public double standardizedItemMaximum(String name)  
Mean value of all item maxima  Raw data  public double rawMeanOfItemMaxima()  
Standardized data  public double standardizedMeanOfItemMaxima()  
Standard deviation of all item maxima  Raw data  public double rawVarianceOfItemMaxima()  
Standardized data  public double standardizedVarianceOfItemMaxima()  
Variance of all item maxima  Raw data  public double rawVarianceOfItemMaxima()  
Standardized data  public double standardizedVarianceOfItemMaxima()  
Maximum of all item maxima  Raw data  public double rawMaximumOfItemMaxima()  
Standardized data  public double standardizedMaximumOfItemMaxima()  
Minimum of all item maxima  Raw data  public double rawMinimumOfItemMaxima()  
Standardized data  public double standardizedMinimumOfItemMaxima()  
Range of all item maxima  Raw data  public double rawRangeOfItemMaxima()  
Standardized data  public double standardizedRangeOfItemMaxima()  
Item minima  Minima of all items  Raw data  public double[] rawItemMinima() 
Standardized data  public double[] standardizedItemMinima()  
Minimum of an individual item  Raw data  public double rawItemMinimum(int index)  
public double rawItemMinimum(String name)  
Standardized data  public double standardizedItemMinimum(int index)  
public double standardizedItemMinimum(String name)  
Mean value of all item minima  Raw data  public double rawMeanOfItemMinima()  
Standardized data  public double standardizedMeanOfItemMinima()  
Standard deviation of all item minima  Raw data  public double rawVarianceOfItemMinima()  
Standardized data  public double standardizedVarianceOfItemMinima()  
Variance of all item minima  Raw data  public double rawVarianceOfItemMinima()  
Standardized data  public double standardizedVarianceOfItemMinima()  
Minimum of all item minima  Raw data  public double rawMinimumOfItemMinima()  
Standardized data  public double standardizedMinimumOfItemMinima()  
Minimum of all item minima  Raw data  public double rawMinimumOfItemMinima()  
Standardized data  public double standardizedMinimumOfItemMinima()  
Range of all item minima  Raw data  public double rawRangeOfItemMinima()  
Standardized data  public double standardizedRangeOfItemMinima()  
Item ranges  Ranges of all items  Raw data  public double[] rawItemRanges() 
Standardized data  public double[] standardizedItemRanges()  
Range of an individual item  Raw data  public double rawItemRange(int index)  
public double rawItemRange(String name)  
Standardized data  public double standardizedItemRange(int index)  
public double standardizedItemRange(String name)  
Mean value of all item ranges  Raw data  public double rawMeanOfItemRanges()  
Standardized data  public double standardizedMeanOfItemRanges()  
Standard deviation of all item ranges  Raw data  public double rawVarianceOfItemRanges()  
Standardized data  public double standardizedVarianceOfItemRanges()  
Variance of all item ranges  Raw data  public double rawVarianceOfItemRanges()  
Standardized data  public double standardizedVarianceOfItemRanges()  
Minimum of all item ranges  Raw data  public double rawMinimumOfItemRanges()  
Standardized data  public double standardizedMinimumOfItemRanges()  
Minimum of all item ranges  Raw data  public double rawMinimumOfItemRanges()  
Standardized data  public double standardizedMinimumOfItemRanges()  
Range of all item ranges  Raw data  public double rawRangeOfItemRanges()  
Standardized data  public double standardizedRangeOfItemRanges()  
Item medians  Medians of all items  Raw data  public double[] rawItemMedians() 
Standardized data  public double[] standardizedItemMedians()  
Median of an individual item  Raw data  public double rawItemMedian(int index)  
public double rawItemMedian(String name)  
Standardized data  public double standardizedItemMedian(int index)  
public double standardizedItemMedian(String name)  
Mean value of all item medians  Raw data  public double rawMeanOfItemMedians()  
Standardized data  public double standardizedMeanOfItemMedians()  
Standard deviation of all item medians  Raw data  public double rawVarianceOfItemMedians()  
Standardized data  public double standardizedVarianceOfItemMedians()  
Variance of all item medians  Raw data  public double rawVarianceOfItemMedians()  
Standardized data  public double standardizedVarianceOfItemMedians()  
Minimum of all item medians  Raw data  public double rawMinimumOfItemMedians()  
Standardized data  public double standardizedMinimumOfItemMedians()  
Minimum of all item medians  Raw data  public double rawMinimumOfItemMedians()  
Standardized data  public double standardizedMinimumOfItemMedians()  
Range of all item medians  Raw data  public double rawRangeOfItemMedians()  
Standardized data  public double standardizedRangeOfItemMedians()  
Item totals  Totals of all items  Raw data  public double[] rawItemTotals() 
Standardized data  public double[] standardizedItemTotals()  
Total of an individual item  Raw data  public double rawItemTotal(int index)  
public double rawItemTotal(String name)  
Standardized data  public double standardizedItemTotal(int index)  
public double standardizedItemTotal(String name)  
Mean value of all item totals  Raw data  public double rawMeanOfItemTotals()  
Standardized data  public double standardizedMeanOfItemTotals()  
Standard deviation of all item totals  Raw data  public double rawVarianceOfItemTotals()  
Standardized data  public double standardizedVarianceOfItemTotals()  
Variance of all item totals  Raw data  public double rawVarianceOfItemTotals()  
Standardized data  public double standardizedVarianceOfItemTotals()  
Minimum of all item totals  Raw data  public double rawMinimumOfItemTotals()  
Standardized data  public double standardizedMinimumOfItemTotals()  
Minimum of all item totals  Raw data  public double rawMinimumOfItemTotals()  
Standardized data  public double standardizedMinimumOfItemTotals()  
Range of all item totals  Raw data  public double rawRangeOfItemTotals()  
Standardized data  public double standardizedRangeOfItemTotals()  
Item Moment Skewness  Moment skewness of all items  Raw data  public double[] rawItemMomentSkewnessess() 
Standardized data  public double[] standardizedItemMomentSkewnessess()  
Moment skewness of an individual item  Raw data  public double rawItemMomentSkewness(int index)  
public double rawItemMomentSkewness(String name)  
Standardized data  public double standardizedItemMomentSkewness(int index)  
public double standardizedItemMomentSkewness(String name)  
Item Median Skewness  Median skewness of all items  Raw data  public double[] rawItemMedianSkewnessess() 
Standardized data  public double[] standardizedItemMedianSkewnessess()  
Median skewness of an individual item  Raw data  public double rawItemMedianSkewness(int index)  
public double rawItemMedianSkewness(String name)  
Standardized data  public double standardizedItemMedianSkewness(int index)  
public double standardizedItemMedianSkewness(String name)  
Item Quartile Skewness  Quartile skewness of all items  Raw data  public double[] rawItemQuartileSkewnessess() 
Standardized data  public double[] standardizedItemQuartileSkewnessess()  
Quartile skewness of an individual item  Raw data  public double rawItemQuartileSkewness(int index)  
public double rawItemQuartileSkewness(String name)  
Standardized data  public double standardizedItemQuartileSkewness(int index)  
public double standardizedItemQuartileSkewness(String name)  
Item Excess Kurtosis  Excess kurtoses of all items  Raw data  public double[] rawItemExcesskurtoses() 
Standardized data  public double[] standardizedItemExcesskurtoses()  
Excess kurtosis of an individual item  Raw data  public double rawItemExcessKurtosis(int index)  
public double rawItemExcessKurtosis(String name)  
Standardized data  public double standardizedItemExcessKurtosis(int index)  
public double standardizedItemExcessKurtosis(String name)  
Item Names and Indices  Names of the used items  public String[] itemNames()  
Item names as entered  public String[] originalItemNames()  
Deleted item names  public String[] deletedItemNames()  
Index of an item  public int itemIndex(String name)  
Name of an item  public String itemName(int index)  
Number of Items  Number of items used  public int usedNumberOfItems()  
Number of items entered  public int originalNumberOfItems()  
Number of items deleted  public int numberOfDeletedItems()  
Person Means  Mean values of all persons  Raw data  public double[] rawPersonMeans() 
Standardized data  public double[] standardizedPersonMeans()  
Mean of an individual person  Raw data  public double rawPersonMean(int index)  
Standardized data  public double standardizedPersonMean(int index)  
Person Standard Deviations  Standard deviations of all persons  Raw data  public double[] rawPersonStandardDeviations() 
Standardized data  public double[] standardizedPersonStandardDeviations()  
Standard deviation of an individual person  Raw data  public double rawPersonStandardDeviation(int index)  
Standardized data  public double standardizedPersonStandardDeviation(int index)  
Person Variances  Variances of all persons  Raw data  public double[] rawPersonVariances() 
Standardized data  public double[] standardizedPersonVariances()  
Variance of an individual person  Raw data  public double rawPersonVariance(int index)  
Standardized data  public double standardizedPersonVariance(int index)  
Person Maxima  Maxima of all persons  Raw data  public double[] rawPersonMaxima() 
Standardized data  public double[] standardizedPersonMaxima()  
Maximum of an individual person  Raw data  public double rawPersonMaximum(int index)  
Standardized data  public double standardizedPersonMaximum(int index)  
Person Minima  Minima of all persons  Raw data  public double[] rawPersonMinima() 
Standardized data  public double[] standardizedPersonMinima()  
Minimum of an individual person  Raw data  public double rawPersonMinimum(int index)  
Standardized data  public double standardizedPersonMinimum(int index)  
Person Ranges  Ranges of all persons  Raw data  public double[] rawPersonRanges() 
Standardized data  public double[] standardizedPersonRanges()  
Range of an individual person  Raw data  public double rawPersonRange(int index)  
Standardized data  public double standardizedPersonRange(int index)  
Person Totals  Totals of all persons  Raw data  public double[] rawPersonTotals() 
Standardized data  public double[] standardizedPersonTotals()  
Total of an individual person  Raw data  public double rawPersonTotal(int index)  
Standardized data  public double standardizedPersonTotal(int index)  
Person Indices  Indices of the used persons  public String[] personIndices()  
Deleted person indices  public String[] deletedPersonsIndices()  
Number of Persons  Number of Persons used  public int usedNumberOfPersons()  
Number of persons entered  public int originalNumberOfPersons()  
Number of persons deleted  public int numberOfDeletedPersons()  
All responses  Mean  Raw data  public double rawAllResponsesMean() 
Standardized data  public double standardizedAllResponsesMean()  
Standard Deviation  Raw data  public double rawAllResponsesStandardDeviation()  
Standardized data  public double standardizedAllResponsesStandardDeviation()  
Variance  Raw data  public double rawAllResponsesVariance()  
Standardized data  public double standardizedAllResponsesVariance()  
Minimum  Raw data  public double rawAllResponsesMinimum()  
Standardized data  public double standardizedAllResponsesMinimum()  
Maximum  Raw data  public double rawAllResponsesMaximum()  
Standardized data  public double standardizedAllResponsesMaximum()  
Range  Raw data  public double rawAllResponsesRange()  
Standardized data  public double standardizedAllResponsesRange()  
Total  Raw data  public double rawAllResponsesTotal()  
Standardized data  public double standardizedAllResponsesTotal()  
Responses  Original responses  as entered  public Object originalScores() 
as row per item  public double[][] originalScoresAsRowPerItem()  
as row per person  public double[][] originalScoresAsRowPerPerson()  
Used responses (Raw data)  as row per item  public double[][] usedScoresAsRowPerItem()  
as row per person  public double[][] usedScoresAsRowPerPerson()  
Used responses (Standardized data)  as row per item  public double[][] standardizedScoresAsRowPerItem()  
as row per person  public double[][] standardizedScoresAsRowPerPerson()  
Replaced responses  item name and person index of replacements  public String[] indicesOfReplacedScores()  
Number of responses  original number  public int originalTotalNumberOfScores()  
number used  public int usedTotalNumberOfScores()  
number deleted  public int numberOfDeletedScores()  
number of missing responses replaced  public int numberOfReplacedScores() 
Format A readScoresAsRowPerPersonA Title Number of items Number of persons Row of item names Matrix of scores arranged as rows starting with the person name then scores for that person with separators, e.g. space, comma. details 
Format B readScoresAsRowPerPersonB Title Number of items Number of persons Row of item names Row of person names Matrix of scores arranged as row per person with separators, e.g. space, comma. details 
Format C readScoresAsRowPerPersonC Scores only Matrix of scores arranged as row per person with separators, e.g. space, comma. details 
Format D readScoresAsRowPerPersonD Scores only Matrix of single character scores arranged as row per person WITHOUT separators, e.g. 1101011 details 
Replaced methods readScoresAsRowPerPerson 
Format A readScoresAsRowPerItemA Title Number of items Number of persons Row of item names Matrix of scores arranged as rows starting with the item name then scores for that item with separators, e.g. space, comma. details 
Format B readScoresAsRowPerItemB Title Number of items Number of persons Row of item names Row of person names Matrix of scores arranged as row per item with separators, e.g. space, comma. details 
Format C readScoresAsRowPerItemC Scores only Matrix of scores arranged as row per item with separators, e.g. space, comma. details 
Format D readScoresAsRowPerItemD Scores only Matrix of single character scores arranged as row per item WITHOUT separators, e.g. 1101011 details 
Replaced methods readScoresAsRowPerItem 