Added classes for binominal distribution and some infrastructure for other

discrete distributions.
Contributed by Brent Worden (brent@worden.org)


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@140993 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/math/distribution/AbstractDiscreteDistribution.java

@@ -0,0 +1,160 @@
+/* ====================================================================
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2003 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Commons", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+package org.apache.commons.math.stat.distribution;
+
+
+/**
+ * Base class for various discrete distributions.  It provides default
+ * implementations for some of the methods that do not vary from distribution
+ * to distribution.
+ *  
+ * @version $Revision: 1.1 $ $Date: 2003/08/16 17:06:15 $
+ */
+public abstract class AbstractDiscreteDistribution
+    implements DiscreteDistribution {
+        
+    /**
+     * Default constructor.
+     */
+    protected AbstractDiscreteDistribution() {
+        super();
+    }
+    
+    /**
+     * For this disbution, X, this method returns P(x0 &le; X &le; x1).
+     * @param x0 the inclusive, lower bound
+     * @param x1 the inclusive, upper bound
+     * @return the cummulative probability. 
+     */
+    public double cummulativeProbability(int x0, int x1) {
+        return cummulativeProbability(x1) - 
+            cummulativeProbability(x0 - 1);
+    }
+    
+    /**
+     * For this distribution, X, this method returns the critical point x, such
+     * that P(X &le; x) &le; <code>p</code>.
+     *
+     * @param p the desired probability
+     * @return x, such that P(X &lt; x) = <code>p</code>
+     */
+    public int inverseCummulativeProbability(final double p) {
+        if (p < 0.0 || p > 1.0) {
+            throw new IllegalArgumentException(
+                "p must be between 0.0 and 1.0, inclusive.");
+        }
+        
+        // by default, do simple bisection.
+        // subclasses can override if there is a better method.
+        int x0 = getDomainLowerBound(p);
+        int x1 = getDomainUpperBound(p);
+        double pm;
+        while (x0 < x1) {
+            int xm = x0 + (x1 - x0) / 2;
+            pm = cummulativeProbability(xm);
+            if (pm > p) {
+                // update x1
+                if (xm == x1) {
+                    // this can happen with integer division
+                    // simply decrement x1
+                    --x1;
+                } else {
+                    // update x1 normally
+                    x1 = xm;
+                }
+            } else {
+                // update x0
+                if (xm == x0) {
+                    // this can happen with integer division
+                    // simply increment x0
+                    ++x0;
+                } else {
+                    // update x0 normally
+                    x0 = xm;
+                }
+            }
+        }
+        
+        // insure x0 is the correct critical point
+        pm = cummulativeProbability(x0);
+        while (pm > p) {
+            --x0;
+            pm = cummulativeProbability(x0);
+        }
+        
+        return x0;        
+    }
+    
+    /**
+     * Access the domain value lower bound, based on <code>p</code>, used to
+     * bracket a PDF root.  This method is used by
+     * {@link #inverseCummulativeProbability(int)} to find critical values.
+     * 
+     * @param p the desired probability for the critical value
+     * @return domain value lower bound, i.e.
+     *         P(X &lt; <i>lower bound</i>) &lt; <code>p</code> 
+     */
+    protected abstract int getDomainLowerBound(double p);
+    
+    /**
+     * Access the domain value upper bound, based on <code>p</code>, used to
+     * bracket a PDF root.  This method is used by
+     * {@link #inverseCummulativeProbability(int)} to find critical values.
+     * 
+     * @param p the desired probability for the critical value
+     * @return domain value upper bound, i.e.
+     *         P(X &lt; <i>upper bound</i>) &gt; <code>p</code> 
+     */
+    protected abstract int getDomainUpperBound(double p);
+}

src/java/org/apache/commons/math/distribution/BinomialDistribution.java

@@ -0,0 +1,94 @@
+/* ====================================================================
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2003 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Commons", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+package org.apache.commons.math.stat.distribution;
+
+/**
+ * The Binomial Distribution.
+ * 
+ * Instances of BinomialDistribution objects should be created using
+ * {@link DistributionFactory#createBinomailDistribution(int, double)}.
+ * 
+ * References:
+ * <ul>
+ * <li><a href="http://mathworld.wolfram.com/BinomialDistribution.html">
+ * Binomial Distribution</a></li>
+ * </ul>
+ * 
+ * @version $Revision: 1.1 $ $Date: 2003/08/16 17:06:15 $
+ */
+public interface BinomialDistribution extends DiscreteDistribution {
+    /**
+     * Access the number of trials for this distribution.
+     * @return the number of trials.
+     */
+    int getNumberOfTrials();
+    
+    /**
+     * Access the probability of success for this distribution.
+     * @return the probability of success.
+     */
+    double getProbabilityOfSuccess();
+    
+    /**
+     * Change the number of trials for this distribution.
+     * @param trials the new number of trials.
+     */
+    void setNumberOfTrials(int trials);
+    
+    /**
+     * Change the probability of success for this distribution.
+     * @param p the new probability of success.
+     */
+    void setProbabilityOfSuccess(double p);
+}

src/java/org/apache/commons/math/distribution/BinomialDistributionImpl.java

@@ -0,0 +1,184 @@
+/* ====================================================================
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2003 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Commons", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+package org.apache.commons.math.stat.distribution;
+
+import org.apache.commons.math.special.Beta;
+import org.apache.commons.math.util.MathUtils;
+
+/**
+ * The default implementation of {@link BinomialDistribution}.
+ * 
+ * @version $Revision: 1.1 $ $Date: 2003/08/16 17:06:15 $
+ */
+public class BinomialDistributionImpl extends AbstractDiscreteDistribution
+    implements BinomialDistribution {
+
+    /** The number of trials. */
+    private int numberOfTrials;
+    
+    /** The probability of success. */
+    private double probabilityOfSuccess;
+    
+    /**
+     * Create a binomial distribution with the given number of trials and
+     * probability of success.
+     * @param trials the number of trials.
+     * @param p the probability of success.
+     */
+    public BinomialDistributionImpl(int trials, double p) {
+        super();
+        setNumberOfTrials(trials);
+        setProbabilityOfSuccess(p);
+    }
+    
+    /**
+     * Access the number of trials for this distribution.
+     * @return the number of trials.
+     */
+    public int getNumberOfTrials() {
+        return numberOfTrials;
+    }
+
+    /**
+     * Access the probability of success for this distribution.
+     * @return the probability of success.
+     */
+    public double getProbabilityOfSuccess() {
+        return probabilityOfSuccess;
+    }
+
+    /**
+     * Change the number of trials for this distribution.
+     * @param trials the new number of trials.
+     */
+    public void setNumberOfTrials(int trials) {
+        if (trials < 0) {
+            throw new IllegalArgumentException(
+                "number of trials must be non-negative.");
+        }
+        numberOfTrials = trials;
+    }
+
+    /**
+     * Change the probability of success for this distribution.
+     * @param p the new probability of success.
+     */
+    public void setProbabilityOfSuccess(double p) {
+        if (p < 0.0 || p > 1.0) {
+            throw new IllegalArgumentException(
+                "probability of success must be between 0.0 and 1.0, inclusive.");
+        }
+        probabilityOfSuccess = p;
+    }
+    
+    /**
+     * Access the domain value lower bound, based on <code>p</code>, used to
+     * bracket a PDF root.
+     * 
+     * @param p the desired probability for the critical value
+     * @return domain value lower bound, i.e.
+     *         P(X &lt; <i>lower bound</i>) &lt; <code>p</code> 
+     */
+    protected int getDomainLowerBound(double p) {
+        return -1;
+    }
+
+    /**
+     * Access the domain value upper bound, based on <code>p</code>, used to
+     * bracket a PDF root.
+     * 
+     * @param p the desired probability for the critical value
+     * @return domain value upper bound, i.e.
+     *         P(X &lt; <i>upper bound</i>) &gt; <code>p</code> 
+     */
+    protected int getDomainUpperBound(double p) {
+        return getNumberOfTrials();
+    }
+
+    /**
+     * For this disbution, X, this method returns P(X &le; x).
+     * @param x the value at which the PDF is evaluated.
+     * @return PDF for this distribution. 
+     */
+    public double cummulativeProbability(int x) {
+        double ret;
+        if (x < 0) {
+            ret = 0.0;
+        } else if (x >= getNumberOfTrials()) {
+            ret = 1.0;
+        } else {
+            ret = 1.0 - Beta.regularizedBeta(getProbabilityOfSuccess(),
+                x + 1.0, getNumberOfTrials() - x);
+        }
+        return ret;
+    }
+
+    /**
+     * For this disbution, X, this method returns P(X = x).
+     * @param x the value at which the PMF is evaluated.
+     * @return PMF for this distribution. 
+     */
+    public double probability(int x) {
+        double ret;
+        if (x < 0 || x > getNumberOfTrials()) {
+            ret = 0.0;
+        } else {
+            ret = MathUtils.binomialCoefficientDouble(getNumberOfTrials(), x) *
+                Math.pow(getProbabilityOfSuccess(), x) *
+                Math.pow(1.0 - getProbabilityOfSuccess(),
+                    getNumberOfTrials() - x);
+        }
+        return ret;
+    }
+}

src/java/org/apache/commons/math/distribution/DiscreteDistribution.java

@@ -0,0 +1,90 @@
+/* ====================================================================
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2003 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Commons", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+package org.apache.commons.math.stat.distribution;
+
+/**
+ * Base interface for various discrete distributions.
+ * 
+ * @version $Revision: 1.1 $ $Date: 2003/08/16 17:06:15 $
+ */
+public interface DiscreteDistribution {
+    /**
+     * For this disbution, X, this method returns P(X = x).
+     * @param x the value at which the PMF is evaluated.
+     * @return PMF for this distribution. 
+     */
+    double probability(int x);
+    
+    /**
+     * For this disbution, X, this method returns P(X &le; x).
+     * @param x the value at which the PDF is evaluated.
+     * @return PDF for this distribution. 
+     */
+    double cummulativeProbability(int x);
+
+    /**
+     * For this disbution, X, this method returns P(x0 &le; X &le; x1).
+     * @param x0 the inclusive, lower bound
+     * @param x1 the inclusive, upper bound
+     * @return the cummulative probability. 
+     */
+    double cummulativeProbability(int x0, int x1);
+    
+    /**
+     * For this disbution, X, this method returns x such that P(X &le; x) <= p.
+     * @param p the cummulative probability.
+     * @return x. 
+     */
+    int inverseCummulativeProbability(double p);
+}

src/java/org/apache/commons/math/distribution/DistributionFactory.java

@@ -57,7 +57,9 @@ package org.apache.commons.math.stat.distribution;
  * This factory provids the means to create common statistical distributions.
  * The following distributions are supported:
  * <ul>
+ * <li>Binomial</li>
  * <li>Chi-Squared</li>
+ * <li>Exponential</li>
  * <li>F</li>
  * <li>Gamma</li>
  * <li>Student's t</li>
@@ -70,7 +72,7 @@ package org.apache.commons.math.stat.distribution;
  * ChiSquaredDistribution chi = factory.createChiSquareDistribution(5.0);
  * </pre>
  * 
- * @version $Revision: 1.9 $ $Date: 2003/07/30 21:58:11 $
+ * @version $Revision: 1.10 $ $Date: 2003/08/16 17:06:15 $
  */
 public abstract class DistributionFactory {
     /**
@@ -90,6 +92,16 @@ public abstract class DistributionFactory {
         return new DistributionFactoryImpl();
     }
 
+    /**
+     * Create a binomial distribution with the given number of trials and
+     * probability of success.
+     * @param numberOfTrials the number of trials.
+     * @param probabilityOfSuccess the probability of success.
+     * @return a new binomial distribution.
+     */
+    public abstract BinomialDistribution createBinomailDistribution(
+        int numberOfTrials, double probabilityOfSuccess);
+        
     /**
      * Create a new chi-square distribution with the given degrees of freedom.
      * @param degreesOfFreedom degrees of freedom.

src/java/org/apache/commons/math/distribution/DistributionFactoryImpl.java

@@ -58,7 +58,7 @@ package org.apache.commons.math.stat.distribution;
  * A concrete distribution factory.  This is the default factory used by
  * Commons-Math.
  *  
- * @version $Revision: 1.7 $ $Date: 2003/07/09 20:03:23 $
+ * @version $Revision: 1.8 $ $Date: 2003/08/16 17:06:15 $
  */
 public class DistributionFactoryImpl extends DistributionFactory {
     /**
@@ -122,4 +122,17 @@ public class DistributionFactoryImpl extends DistributionFactory {
         return new ExponentialDistributionImpl(mean);
     }    
 
+    /**
+     * Create a binomial distribution with the given number of trials and
+     * probability of success.
+     * @param numberOfTrials the number of trials.
+     * @param probabilityOfSuccess the probability of success.
+     * @return a new binomial distribution.
+     */
+    public BinomialDistribution createBinomailDistribution(
+        int numberOfTrials, double probabilityOfSuccess) {
+        return new BinomialDistributionImpl(numberOfTrials,
+            probabilityOfSuccess);
+    }
+
 }

src/test/org/apache/commons/math/distribution/BinomialDistributionTest.java

@@ -0,0 +1,163 @@
+/* ====================================================================
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2003 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Commons", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+package org.apache.commons.math.stat.distribution;
+
+import junit.framework.TestCase;
+
+/**
+ * @author Brent Worden
+ */
+public class BinomialDistributionTest extends TestCase {
+    private BinomialDistribution b;
+    
+    /**
+     * Constructor for ChiSquareDistributionTest.
+     * @param name
+     */
+    public BinomialDistributionTest(String name) {
+        super(name);
+    }
+
+    /*
+     * @see TestCase#setUp()
+     */
+    protected void setUp() throws Exception {
+        super.setUp();
+        b = DistributionFactory.newInstance().createBinomailDistribution(10, 0.70);
+    }
+
+    /*
+     * @see TestCase#tearDown()
+     */
+    protected void tearDown() throws Exception {
+        b = null;
+        super.tearDown();
+    }
+
+    public void testInverseCummulativeProbability001() {
+        testValue(1, .001);
+    }
+    
+    public void testInverseCumulativeProbability010() {
+        testValue(2, .010);
+    }
+    
+    public void testInverseCumulativeProbability025() {
+        testValue(3, .025);
+    }
+
+    public void testInverseCumulativeProbability050() {
+        testValue(4, .050);
+    }
+    
+    public void testInverseCumulativeProbability100() {
+        testValue(4, .100);
+    }
+
+    public void testInverseCummulativeProbability999() {
+        testValue(9, .999);
+    }
+    
+    public void testInverseCumulativeProbability990() {
+        testValue(9, .990);
+    }
+    
+    public void testInverseCumulativeProbability975() {
+        testValue(9, .975);
+    }
+
+    public void testInverseCumulativeProbability950() {
+        testValue(8, .950);
+    }
+    
+    public void testInverseCumulativeProbability900() {
+        testValue(8, .900);
+    }
+
+    public void testCummulativeProbability1() {
+        testProbability(1, .00014);
+    }
+    
+    public void testCumulativeProbability2() {
+        testProbability(2, .00159);
+    }
+    
+    public void testCumulativeProbability3() {
+        testProbability(3, .01059);
+    }
+
+    public void testCumulativeProbability4() {
+        testProbability(4, .04735);
+    }
+    
+    public void testCumulativeProbability9() {
+        testProbability(9, .97175);
+    }
+
+    public void testCummulativeProbability8() {
+        testProbability(8, .85069);
+    }
+    
+    private void testProbability(int x, double expected){
+        double actual = b.cummulativeProbability(x);
+        assertEquals(expected, actual, 10e-4);
+    }
+    
+    private void testValue(int expected, double p){
+        int actual = b.inverseCummulativeProbability(p);
+        assertEquals(expected, actual);
+        assertTrue(b.cummulativeProbability(actual) <= p);
+        assertTrue(b.cummulativeProbability(actual + 1) >= p);
+    }
+}

src/test/org/apache/commons/math/distribution/DistributionFactoryImplTest.java

@@ -197,4 +197,60 @@ public class DistributionFactoryImplTest extends TestCase {
             fail("positive degrees of freedom.  IllegalArgumentException is not expected");
         }
     }
+    
+    public void testBinomialDistributionNegativePositive(){
+        try {
+            factory.createBinomailDistribution(-1, 0.5);
+            fail("negative number of trials.  IllegalArgumentException expected");
+        } catch (IllegalArgumentException ex ) {
+        }
+    }
+    
+    public void testBinomialDistributionZeroPositive(){
+        try {
+            factory.createBinomailDistribution(0, 0.5);
+        } catch (IllegalArgumentException ex ) {
+            fail("zero number of trials.  IllegalArgumentException is not expected");
+        }
+    }
+    
+    public void testBinomialDistributionPositivePositive(){
+        try {
+            factory.createBinomailDistribution(10, 0.5);
+        } catch (IllegalArgumentException ex ) {
+            fail("positive number of trials.  IllegalArgumentException is not expected");
+        }
+    }
+    
+    public void testBinomialDistributionPositiveNegative(){
+        try {
+            factory.createBinomailDistribution(10, -0.5);
+            fail("negative probability of success.  IllegalArgumentException expected");
+        } catch (IllegalArgumentException ex ) {
+        }
+    }
+    
+    public void testBinomialDistributionPositiveZero(){
+        try {
+            factory.createBinomailDistribution(10, 0.0);
+        } catch (IllegalArgumentException ex ) {
+            fail("zero probability of success.  IllegalArgumentException is not expected");
+        }
+    }
+    
+    public void testBinomialDistributionPositiveOne(){
+        try {
+            factory.createBinomailDistribution(10, 1.0);
+        } catch (IllegalArgumentException ex ) {
+            fail("valid probability of success.  IllegalArgumentException is not expected");
+        }
+    }
+    
+    public void testBinomialDistributionPositiveTwo(){
+        try {
+            factory.createBinomailDistribution(10, 2.0);
+            fail("high probability of success.  IllegalArgumentException expected");
+        } catch (IllegalArgumentException ex ) {
+        }
+    }
 }