I am trying to work out the standard deviation and RSD of a set of percentages. The percentages refer to the sellthrough of products across a number of stores e.g.
Product 1
Store 1 - Opening stock - 10, sold - 7, 70% sold.
Store 2 - Opening stock - 20, sold - 14, 70% sold.
Store 3 - Opening stock - 30, sold - 21, 70% sold.
Store 4 - Opening stock - 40, sold - 20, 50% sold.
Is it fair to say that the standard deviation of the % sold = 0.1 and the RSD = 15% or is there a different method or interpretation when performing calculation of SD & RSD on a set of percentages? Should I be applying a weighting before calculating the mean?
The goal is to identify which stores perform well or not so well with certain products or within certain ranges of products. The opening stock will vary in each case, in reality the difference would be thousands of units between stores and thousands of units in sales.
I appreciate any feedback. Thanks.