edu.uah.math.distributions
Class BirthdayDistribution

java.lang.Object
  edu.uah.math.distributions.Distribution
      edu.uah.math.distributions.BirthdayDistribution

All Implemented Interfaces:

java.io.Serializable

public class BirthdayDistribution
extends Distribution
implements java.io.Serializable

This class models the distribution of the number of distinct sample values when a sample of a specified size is chosen with replacement from a finite population of a specified size.

Version:

August, 2003

Author:

Kyle Siegrist, Dawn Duehring

See Also:

Serialized Form

Field Summary

Fields inherited from class edu.uah.math.distributions.Distribution

CONTINUOUS, DISCRETE, MIXED

Constructor Summary

BirthdayDistribution()
This default constructor creates a new birthday distribution with population size 365 (the classical birthday problem) and sample size 20.

BirthdayDistribution(int n, int k)
This general constructor creates a new birthday distribution with a specified population size and sample size.

Method Summary

double	getDensity(double x) This method computes the probability density function.
double	getMean() This method computes the mean of the distribution in terms of the parameters.
int	getPopulationSize() This method returns the population size.
int	getSampleSize() This method returns the sample size.
double	getVariance() This method computes the variance of the distribution in terms of the parameters.
void	setParameters(int n, int k) This method sets the parameters: the population size and the sample size.
void	setPopulationSize(int n) This method sets the population size.
void	setSampleSize(int k) This method sets the sample size.
double	simulate() This method simulates a value from the distribution.
java.lang.String	toString() This method returns a string that gives the name of the distribution and the values of the parameters.

Methods inherited from class edu.uah.math.distributions.Distribution

getCDF, getDomain, getFailureRate, getMaxDensity, getMedian, getMGF, getMoment, getMoment, getPGF, getQuantile, getSD, getType, setDomain, setDomain

Methods inherited from class java.lang.Object

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

Constructor Detail

BirthdayDistribution

public BirthdayDistribution(int n,
                            int k)

This general constructor creates a new birthday distribution with a specified population size and sample size.

Parameters:

n - the population size

k - the sample size

BirthdayDistribution

public BirthdayDistribution()

This default constructor creates a new birthday distribution with population size 365 (the classical birthday problem) and sample size 20.

Method Detail

setParameters

public void setParameters(int n,
                          int k)

This method sets the parameters: the population size and the sample size. Also, the probabilities are computed and stored in an array, and the domain computed.

Parameters:

n - the population size

k - the sample size

getDensity

public double getDensity(double x)

This method computes the probability density function.

Specified by:

getDensity in class Distribution

Parameters:

x - a number in the domain of the distribuiton

Returns:

the probability density at x

getMean

public double getMean()

This method computes the mean of the distribution in terms of the parameters.

Overrides:

getMean in class Distribution

Returns:

the mean

getVariance

public double getVariance()

This method computes the variance of the distribution in terms of the parameters.

Overrides:

getVariance in class Distribution

Returns:

the variance

getPopulationSize

public int getPopulationSize()

This method returns the population size.

Returns:

the population size

setPopulationSize

public void setPopulationSize(int n)

This method sets the population size.

Parameters:

n - the population size

getSampleSize

public int getSampleSize()

This method returns the sample size.

Returns:

the sample size

setSampleSize

public void setSampleSize(int k)

This method sets the sample size.

Parameters:

k - the sample size

simulate

public double simulate()

This method simulates a value from the distribution. This is done by simulating a random sample from the population, and computing the number of distinct sample values.

Overrides:

simulate in class Distribution

Returns:

a simulated value from the distribution

toString

public java.lang.String toString()

This method returns a string that gives the name of the distribution and the values of the parameters.

Overrides:

toString in class Distribution

Returns:

a string giving the name of the distribution and the values of the parameters