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Thread: How to calculate Standard Deviation

  1. #1

    Thread Starter
    Addicted Member
    Join Date
    Apr 2009
    Posts
    175

    How to calculate Standard Deviation

    Can someone help me, Iam trying to calculate the standard Deviation.
    here is part of the code that I am using.
    Dim dSum As Double
    Dim lCol As Long, lRow As Long

    Dim mean As Double
    Dim mean2 As Double

    Dim sdA As Double
    lCol = 4 ' The column you want to sum
    With Grid1
    For lRow = .FixedRows To .Rows - 1 ' Process all rows except fixed ones
    If .TextMatrix(lRow, lCol) = "" Then
    GoTo final
    Else

    dSum = dSum + CDbl(.TextMatrix(lRow, lCol)) 'Suma la la ultima columna a la anterior
    average1 = Round(dSum / Valor, 2)

    txtAvarage = average1
    End If
    Next lRow
    End With
    final:
    Call calculateSD

    End Sub
    Private Sub calculateSD()
    Dim lrows As Integer
    Dim sd As Double
    With Grid1
    For lrows = .FixedRows To .Rows - 1
    If .TextMatrix(lrows, 4) = "" Then
    Exit Sub
    Else
    sd = (CDbl(.TextMatrix(lrows, 4)) - average1) ^ 2

    sd = sd + (CDbl(.TextMatrix(lrows, 4)) - average1) ^ 2
    txtSD = Sqr(sd)

    End If

    Next
    End With
    End Sub

  2. #2
    Frenzied Member
    Join Date
    Mar 2008
    Posts
    1,139

    Re: How to calculate Standard Deviation

    Try;

    Code:
    Private Sub Form_Load()
    
        Dim MyArray As Variant
        Dim x#, sx#, sx2#, cnt#
        
        AutoRedraw = True
        
        'set up demodata
        MyArray = Array(Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd(), Rnd())
        
        'get/ asssign data
        For i = 0 To UBound(MyArray)
            cnt = cnt + 1
            x = MyArray(i)
            Print x
            sx = sx + x
            sx2 = sx2 + x * x
        Next
        
        'report results
        Print "average: " & sx / cnt
        Print "sd: " & Sqr((cnt * sx2 - (sx * sx)) / (cnt * (cnt - 1)))
        
        Height = (Height - ScaleHeight) + CurrentY + TextHeight("I")
    
    End Sub

  3. #3
    PowerPoster Code Doc's Avatar
    Join Date
    Mar 2007
    Location
    Omaha, Nebraska
    Posts
    2,355

    Re: How to calculate Standard Deviation

    http://en.wikipedia.org/wiki/Standard_deviation
    Perhaps you should review this again before you write code.
    Doctor Ed

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