com.itemanalysis.psychometrics.statistics.NormalScores.java Source code

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Here is the source code for com.itemanalysis.psychometrics.statistics.NormalScores.java

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/*
 * Copyright 2012 J. Patrick Meyer
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.itemanalysis.psychometrics.statistics;

import org.apache.commons.math3.distribution.NormalDistribution;

/**
 *
 * @author J. Patrick Meyer
 */
public class NormalScores {

    NormalDistribution norm = null;

    public NormalScores() {
        norm = new NormalDistribution();
    }

    public double blom(double rank, double n) {
        double p = (rank - 3.0 / 8.0) / (n + 1.0 / 4.0);
        return norm.inverseCumulativeProbability(p);
    }

    public double tukey(double rank, double n) {
        double p = (rank - 1.0 / 3.0) / (n + 1.0 / 3.0);
        return norm.inverseCumulativeProbability(p);
    }

    public double vanderWaerden(double rank, double n) {
        double p = rank / (n + 1.0);
        return norm.inverseCumulativeProbability(p);
    }

}