org.statcato.statistics.inferential

Class CI2PopMeanSigmaUnknown

java.lang.Object

org.statcato.statistics.inferential.ConfidenceInterval

org.statcato.statistics.inferential.CI2PopMeanSigmaUnknown

public class CI2PopMeanSigmaUnknown
extends ConfidenceInterval

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

Since:

1.0

Constructor Summary

Constructors

Constructor and Description
CI2PopMeanSigmaUnknown(double confidenceLevel, int n1, int n2, double xBar1, double xBar2, double s1, double s2, boolean varEqual) Constructor

Method Summary

Modifier and Type	Method and Description
double	criticalValue() Returns the critical value corresponding to the given confidence level.
int	DOF() Returns the degrees of freedom.
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

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

CI2PopMeanSigmaUnknown

public CI2PopMeanSigmaUnknown(double confidenceLevel,
                              int n1,
                              int n2,
                              double xBar1,
                              double xBar2,
                              double s1,
                              double s2,
                              boolean varEqual)

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

s1 - sample standard deviation 1

s2 - sample standard deviation 2

varEqual - whether the population variances are assumed to be equal

Method Detail

marginOfError

public double marginOfError()

Returns the margin of error. If population variances are assumed equal, E = t_(alpha/2) * sqrt(sp^2 / n1 + sp^2 / n2), where sp^2 = [(n1 - 1)*s1^2 + (n2 - 1)*s2^2] / [n1 + n2 - 2] If population variances are not assumed equal, E = t_(alpha/2) * sqrt(s1^2 / n1 + s2^2 / 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

DOF

public int DOF()

Returns the degrees of freedom.

Returns:

degrees of freedom