org.statcato.statistics.inferential
Class CI2PopMeanSigmaKnown

java.lang.Object
  extended by org.statcato.statistics.inferential.ConfidenceInterval
      extended by org.statcato.statistics.inferential.CI2PopMeanSigmaKnown

public class CI2PopMeanSigmaKnown
extends ConfidenceInterval

Confidence interval class for two population mean, sigma (population standard deviation) known.

Since:
1.0
Version:
%I%, %G%
Author:
Margaret Yau

Field Summary
 
Fields inherited from class org.statcato.statistics.inferential.ConfidenceInterval
center, confidenceLevel
 
Constructor Summary
CI2PopMeanSigmaKnown(double confidenceLevel, int n1, int n2, double xBar1, double xBar2, double sigma1, double sigma2)
          Constructor
 
Method Summary
 double criticalValue()
          Returns the critical value corresponding to the given confidence level.
 double marginOfError()
          Returns the margin of error.
 
Methods inherited from class org.statcato.statistics.inferential.ConfidenceInterval
center, lowerLimit, toString, upperLimit
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

CI2PopMeanSigmaKnown

public CI2PopMeanSigmaKnown(double confidenceLevel,
                            int n1,
                            int n2,
                            double xBar1,
                            double xBar2,
                            double sigma1,
                            double sigma2)
Constructor

Parameters:
confidenceLevel - confidence level, between 0 and 1
n1 - sample size 1
n2 - sample size 2
xBar1 - sample mean 1
xBar2 - sample mean 2
sigma1 - population standard deviation 1
sigma2 - population standard deviation 2
Method Detail

marginOfError

public double marginOfError()
Returns the margin of error. E = z_(alpha/2) * sqrt(sigma1^2 / n1 + sigma2^2 / n2)

Specified by:
marginOfError in class ConfidenceInterval
Returns:
margin of error

criticalValue

public double criticalValue()
Returns the critical value corresponding to the given confidence level. Uses Student's t distribution to find t_(alpha/2), where alpha is the significance level (1 - confidence level).

Specified by:
criticalValue in class ConfidenceInterval
Returns:
critical value