Variance and Standard Deviation are two statistical calculations that are frequently used to analyze data. The formulae below derive Variance and Standard Deviation:
To find the Standard Deviation of a set of records, use the following technique. In this example, there are two Relations: one Relation with one record per sample set, and another Relation to store the samples. In the Relation which contains the sample records, create a "Sub-Average" Abacus:
Also create an Abacus to calculate the square of the difference between the sample value and the Sub-Average (Mean Diff. Sq.):
In the "Sample Set" Relation, create:
1. An Abacus to find the Sub-Count (n) of the sample records:
2. An Abacus to find the Sub-Total of the Mean Diff. Sq. Abacus:
3. An Abacus to calculate the Variance:
4. An Abacus to calculate the Standard Deviation:
Place the "Variance" and "Standard Deviation" Abacii on the forms in the "Sample Set" Relation where you wish to view this information.