/*
Copyright (C) 2001 Kyle Siegrist, Dawn Duehring
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your option)
any later version.
This program is distributed in the hope that it will be useful, but without
any warranty; without even the implied warranty of merchantability or
fitness for a particular purpose. See the GNU General Public License for
more details. You should have received a copy of the GNU General Public
License along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
package distributions;
/** This class models the distribution of the k'th order statistic for a sample of size n
chosen without replacement from {1, 2, ..., N} .*/
public class FiniteOrderStatisticDistribution extends Distribution{
Distribution dist;
private int sampleSize, populationSize, order;
/**This general constructor creates a new finite order statistic distribution with specified
population and sample sizes, and specified order.*/
public FiniteOrderStatisticDistribution(int N, int n, int k){
setParameters(N, n, k);
}
/**This default constructor creates a new finite order statistic distribution with population
size 50, sample size 10, and order 5.*/
public FiniteOrderStatisticDistribution(){
this(50, 10, 5);
}
/**This method sets the parameters: the sample size, population size, and order.*/
public void setParameters(int N, int n, int k){
populationSize = N;
sampleSize = n;
order = k;
super.setParameters(order, populationSize - sampleSize + order, 1, Distribution.DISCRETE);
}
/**This method computes the getDensity.*/
public double getDensity(double x){
int i = (int)Math.rint(x);
return comb(i - 1, order - 1)
* comb(populationSize - i, sampleSize - order) / comb(populationSize, sampleSize);
}
/**This method computes the mean.*/
public double getMean(){
return (double)order * (populationSize + 1) / (sampleSize + 1);
}
/**This method computes the variance.*/
public double getVariance(){
return (double)(populationSize + 1) * (populationSize - sampleSize)
* order * (sampleSize + 1 - order) / ((sampleSize + 1) * (sampleSize + 1) * (sampleSize + 2));
}
/**This method sets the population size.*/
public void setPopulationSize(int N){
setParameters(N, sampleSize, order);
}
/**This method returns the population size.*/
public int getPopulationSize(){
return populationSize;
}
/**This method sets the sample size.*/
public void setSampleSize(int n){
setParameters(populationSize, n, order);
}
/**This method returns the sampleSize.*/
public int getSampleSize(){
return sampleSize;
}
/**This method sets the order.*/
public void setOrder(int k){
setParameters(populationSize, sampleSize, k);
}
/**This method returns the order.*/
public int getOrder(){
return order;
}
}