# How to ... calculate a customized statistic calculation from the standard statistics (OpenLAB CDS Intelligent Reporting)

A customer had to use the following formula to calculate the "variance"  of his repeated injection:

a = Peak area

a(1)  -   a(2)

Variance(custom) =  ---------------------  x  100

a(mean)

The result can easily be calculated by multiplying the RSTDEV by  1.41421  and applying the % number format (which will multiply the result by 100)

The attached document shows the proof of equivalence.

(originally posted in OpenLAB Forum: https://zohodiscussions.com/openlabcdsforum#Topic/68030000000021001

2012 June 27  by )