Sum Product

See also: ModelRisk functions and windows,

The Sum Product function calculates the sum of N terms, in which each term is the product of some sampled random values.

For example, say you want to model 20 (=N) customers, that each generate a revenue of $ModPERT(0,100,200,2), with a profit margin of Beta(8,2). This would be modeled with a Sum Product calculation.

To see the output functions of this window, click here.

Window elements

In the N field, you can enter the number of terms to be summed. This should be a positive integer value. This can be dynamically linked to a spreadsheet cell (as you will often want to do).

In the Distributions field, you can insert the Distribution Object that will be sampled from in constructing the terms. These can be selected from a list, or from the spreadsheet. A new distribution is added by clicking anywhere in the white space. You can remove a distribution by clicking the X button below the field. Note that at least one distribution should be specified, but there is no upper limit on the number of distributions.

In the Chart options region, you can provide the number of samples to be drawn for the preview graphs, and the number of bars (or "bins") these should be grouped in for the histogram plot.

Two preview graphs are shown. With the M and C buttons, you can switch between viewing cumulative or normal (probability density/mass) graphs.

With the generate button you can generate a new set of random values of the Sum Product distribution.

On top is the graph of the selected distribution (marked with the blue arrow in front of it). Below is a histogram plot with samples generated from the Sum Product distribution.

 

 

 

 

 

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