There are two main methods of calculating standard deviations.

1)The first method is referred to as "The standard deviation of the sample".

2)The second method (the one we are using) is called the "Sample standard deviation".

Our research tells us that the most correct one to use in a case like lottery drawings is the second one. The difference between the two is whether you divide the final sum by the drawsize or by the drawsize less one. We're using the draw size less 1.

Relative to the results, the two methods should not be much different. They are just scaled slightly differently but relative to each other that difference is irrelevant. If you ordered the drawings based on each method the drawings would be in EXACTLY the same order. The whole point of using the standard deviation is to order the drawings in that order. The exact values of each drawing does not have any independent meaning, so the method used to calculate standard deviation really does not matter as long as the same method is consistently used.

Also see: Lotto Terms Glossary definition for standard deviation.