How can I distribute a number of values Normally in Excel VBA

Question

Hi All,

Sorry I know the question isnt as specific as it could be. I am currently working on a replenishment forecasting system for a clothing company (dont ask why it's in VBA). The module I am currently working on is distribution forecasts down to a size level. The idea is that the planners can forecast the number to sell, then can specify a ratio between the sizes.

In order to make the interface a bit nicer I was going to give them 4 options; Assess trend, manual entry, Poisson and Normal. The last two is where I am having an issue. Given a mean and SD I'd like to drop in a ratio (preferably as %s) between the different sizes. The number of the sizes can vary from 1 to ~30 so its going to need to be a calculation.

If anyone could point me towards a method I'd be etenaly greatfull - likewise if you have suggestions for a better method.

Cheers

Answer 1

Here's how to generate Poisson random samples. You can generate normal random samples using the Box-Mueller transform.

Answer 2

For the sake of anyone searching this, whilst only a temporary solution I used probability mass functions to get ratios this allowed the user to modify the mean and SD and thus skew the curve as they wished. I could then use the ratios for my calculations. Poisson also worked with this method but turned out to be a slightly stupid idea in terms of choice.