Standard Deviation and Mean
This example is a relatively easy one. The objective is to compute the mean and the standard deviation from an array. In this example, the array is from A1 to A10 of Sheet1 of an opened Excel Workbook. This program has two Function procedures and one Sub procedure. The sub procedure reads in the numbers from the array (A1..A10), calls up the function procedures and returns the mean and standard deviation value. The mean and standand deviation formulas are shown below. Note that the standard deviation in this example is for a sample, not a population.

Check out Median in the Bootstrap example.  Also see Skew and Kurtosis.
'***********************************************************************
'*                                                       Mean                                                  *
'***********************************************************************

Function Mean(k As Long, Arr() As Single)
Dim Sum As Single
Dim i As Integer

Sum = 0
For i = 1 To k
Sum = Sum + Arr(i)
Next i

Mean = Sum / k

End Function

'************************************************************************
'*                                              Standard Deviation                                    *
'************************************************************************

Function StdDev(k As Long, Arr() As Single)
Dim i As Integer
Dim avg As Single, SumSq As Single

avg = Mean(k, Arr)
For i = 1 To k
SumSq = SumSq + (Arr(i) - avg) ^ 2
Next i

StdDev = Sqr(SumSq / (k - 1))

End Function

'*************************************************************************
'*                                                    Computation                                           *
'*************************************************************************

Sub compute()
Dim Arr(10) As Single
Dim Average As Single
Dim Std_Dev As Single

For i = 1 To 10
Arr(i) = Sheets("Sheet1").Cells(i, 1)
Next i

Average = Mean(10, Arr)
Std_Dev = StdDev(10, Arr)
Sheets("Sheet1").Cells(12, 1) = Average
Sheets("Sheet1").Cells(13, 1) = Std_Dev

End Sub
VBA Codes