Enterprise Edition Only Feature. This method performs a T Test using Students distribution (T distribution) with unequal variances.

This analysis tool and its formulas perform a two-sample student's t-test. This t-test form assumes that the variances of both ranges of data are unequal; it is referred to as a heteroscedastic t-test. You can use a t-test to determine whether two sample means are equal. Use this test when the groups under study are distinct. Use a paired test when there is one group before and after a treatment.

Syntax

Visual Basic (Declaration)
Public Function TTestUnEqualVariances( _ ByVal hypothesizedMeanDifference As Double, _ ByVal probability As Double, _ ByVal firstInputSeriesName As String, _ ByVal secondInputSeriesName As String _ ) As TTestResult

Visual Basic (Declaration)

Public Function TTestUnEqualVariances( _
   ByVal hypothesizedMeanDifference As Double, _
   ByVal probability As Double, _
   ByVal firstInputSeriesName As String, _
   ByVal secondInputSeriesName As String _
) As TTestResult

Visual Basic (Usage) Copy Code

Visual Basic (Usage)	Copy Code
`Dim instance As Statistics Dim hypothesizedMeanDifference As Double Dim probability As Double Dim firstInputSeriesName As String Dim secondInputSeriesName As String Dim value As TTestResult value = instance.TTestUnEqualVariances(hypothesizedMeanDifference, probability, firstInputSeriesName, secondInputSeriesName)`

Dim instance As Statistics
Dim hypothesizedMeanDifference As Double
Dim probability As Double
Dim firstInputSeriesName As String
Dim secondInputSeriesName As String
Dim value As TTestResult
 
value = instance.TTestUnEqualVariances(hypothesizedMeanDifference, probability, firstInputSeriesName, secondInputSeriesName)

C#
public TTestResult TTestUnEqualVariances( double hypothesizedMeanDifference, double probability, string firstInputSeriesName, string secondInputSeriesName )

Parameters

hypothesizedMeanDifference: The hypothesized difference between the means of the data groups.
Hypothesized Mean Difference
probability: The alpha value (probability that the hypothesis is rejected).
Probability
firstInputSeriesName: The name of the Series object that stores the first group of data. Data must be stored in the first Y-values of the series' data points.
First Input Series Name
secondInputSeriesName: The name of the Series object that stores the second group of data. Data must be stored in the first Y-values of the series' data points.
Second Input Series Name

Return Value

Returns Result class from T Test

Example

The following sample performs a t test with unequal variances for two groups of data represented by Series1 and Series2. The results are returned in a TTestResult object.

Visual Basic	Copy Code
`Imports Dundas.Charting.WebControl<CRLF>...<CRLF><CRLF>' Perform the test<CRLF>Dim result As TTestResult = Chart1.DataManipulator.Statistics.TTestUnEqualVariances(0.2,0.05,"Series1","Series2")`

C#	Copy Code
`using Dundas.Charting.WebControl;<CRLF>...<CRLF><CRLF>// Perform the test<CRLF>TTestResult result = Chart1.DataManipulator.Statistics.TTestUnEqualVariances(0.2,0.05,"Series1","Series2");`

Remarks

This method performs a T test for two groups of data, and assumes unequal variances between the two groups (i.e. series).

This analysis tool is referred to as a heteroscedastic t-test, and can be used when the groups under study are distinct. Use a paired test when there is one group before and after a treatment.

If either input series does not exist in the series collection at the time of the method call an exception will be thrown.

The following is a brief description of the TTestResult class members:

Member	Description
FirstSeriesMean	The mean of the first data group.
SecondSeriesMean	The mean of the second data group.
FirstSeriesVariance	The variance of the first data group.
SecondSeriesVariance	The variance of the second data group.
TValue	The T value.
DegreeOfFreedom	The degree of freedom.
ProbabilityTOneTail	Probability - T value (one tail).
TCriticalValueOneTail	T critical value (one tail).
ProbabilityTTwoTail	Probability - T value (two tail).
TCriticalValueTwoTail	T critical value (two tail).

Requirements

Target Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, Windows Vista, Windows Server 2008 family