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
- Version:
- %I%, %G%
- Author:
- Margaret Yau
Constructor Summary |
CI2PopMeanSigmaUnknown(double confidenceLevel,
int n1,
int n2,
double xBar1,
double xBar2,
double s1,
double s2,
boolean varEqual)
Constructor |
Method Summary |
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 java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
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 1n1
- sample size 1n2
- sample size 2xBar1
- sample mean 1xBar2
- sample mean 2s1
- sample standard deviation 1s2
- sample standard deviation 2varEqual
- whether the population variances are assumed to be equal
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