Stdev
The Standard Deviation of the selection.
The Standard Deviation is a measure of how spread out numbers are in a set. The Deviation just means how far from the normal.
Stdev is used when the group of numbers being evaluated is only a partial sampling of the whole population.
The formula:
Where is the mean computed by getting the sum of all the items and dividing them by the number of items minus one.
Sample 1
Given a set of numbers like 12, 6, 12.
Steps:
1. Compute the mean of the sample.
Mean = (Sum of items/n), where n is the number of items
12+6+12/3=10
2. Square the difference between each point and the mean
(1210)^2 =4
(610)^2 =16
(1210)^2 =4
3. Calculate the average of the results in step 2 above
4+16+4/31=24/2
4. Compute the square root of the result in step 4.
√12 or 3.4641
Sample 2:
Given the following sample fields:
Number 
Arbitrary 
Negative Values 
Positive Values 
One 
Binary 
Currency 
Decimal 
1 
3 
1 
1 
1 
0 
$1.00 
1.01 
2 
2 
2 
2 

1 
$10.00 
2.02 
3 
1 
3 
3 

0 
$100.00 
3.03 
4 
0 
4 
4 

1 
$1,000.00 
4.04 
5 
1 
5 
5 

0 
$10,000.00 
5.05 
6 
2 
6 
6 

1 
$1.00 
6.06 
7 
3 
7 
7 

0 
$10.00 
7.07 
8 
0 
8 
8 


$100.00 
8.08 
9 
0 
9 
9 


$1,000.00 
9.09 
10 
0 
10 
0 


$0.00 
0.00 
Sample fields.
The Stdev for each field:
Number 
Arbitrary 
Negative Values 
Positive Values 
One 
Binary 
Currency 
Decimal 
3.0277 
1.7638 
3.0277 
3.0277 
0 
.5345 
$3,197.5720 
3.0579 
The results per field.