This topic introduces the StandardErrorCalculator which is part of the Infragistics Math Calculators™ library and explains, with code examples, how to use it to calculate standard error for a set of numbers.
The topic is organized as follows:
Assembly Requirements
Data Requirements
standard error estimates is the standard deviation of the sampling distribution of the mean. The standard error of a sample depends on the sample size and the larger the size of sample the smaller the standard error.
In sample statistics, standard error is computed by dividing the sample standard deviation by the square root of the size of sample (the total count of numbers). The samples standard deviation is computed by taking square root of the sum of squared differences between the variables and the the mean (refer to the Infragistics Mean Calculator topic) divided by one less than the total count of numbers in the data set.
Figure 1 – Formula for Standard Error Calculation
This section provides a list of properties of the StandardErrorCalculator class.
In order to use the StandardErrorCalculator, the following NuGet package must be added to a WPF project.
Infragistics.WPF.Math.Calculators
For more information on setting up the NuGet feed and adding NuGet packages, you can take a look at the following documentation: NuGet Feeds.
The StandardErrorCalculator uses ItemsSource property for data binding and ValueMemberPath property for data mapping. Any object that meets the following requirements can be bound to this property:
The data model must implement IEnumerable interface (e.g. List, Collection, Queue, Stack)
The data model must contain items that have at least one numeric data column for calculating the standard error.
An example of object that meets above criteria is presented in the following code snippet:
In Visual Basic:
Imports System.Collections.Generic
'...
Public Class DataPointList
Inherits List(Of DataPoint)
Public Sub New(dataValues As IEnumerable(Of Double))
For Each value As Double In dataValues
Me.Add(New DataPoint() With { Key .Value = value })
Next
End Sub
End Class
Public Class DataPoint
Public Property Value() As Double
Get
Return _value
End Get
Set
_value = Value
End Set
End Property
Private _value As Double
End Class
In C#:
using System.Collections.Generic;
//...
public class DataPointList : List<DataPoint>
{
public DataPointList(IEnumerable<double> dataValues)
{
foreach (double value in dataValues)
{
this.Add(new DataPoint { Value = value});
}
}
}
public class DataPoint
{
public double Value { get; set; }
}
This example demonstrates how to calculate standard error for a set of numbers using the StandardErrorCalculator. The StandardErrorCalculator is a non-visual element and it should be defined in resources section on application, page, control level, or in code-behind, the same way as you would define a data source or a variable. Also, refer to the Series Error Bars topic for examples on how to integrate the StandardErrorCalculator with the xamDataChart™ control in order to calculate error bars for Series objects.
In Visual Basic:
Imports Infragistics.Math.Calculators
'...
Dim data As New DataPointList(New List(Of Double)() From { 5.0, 1.0, 2.0, 3.0, 4.0 })
Dim calculator As New StandardErrorCalculator()
calculator.ValueMemberPath = "Value"
calculator.ItemsSource = data
Dim standardError As Double = calculator.Value
In C#:
using Infragistics.Math.Calculators;
//...
DataPointList data = new DataPointList(new List<double> { 5.0, 1.0, 2.0, 3.0, 4.0 });
StandardErrorCalculator calculator = new StandardErrorCalculator();
calculator.ValueMemberPath = "Value";
calculator.ItemsSource = data;
double standardError = calculator.Value;