Color coding model elements for clarity

See also: Model design introduction, Using range names for model clarity, Building models that are efficient, Building models that are easy to check and modify

At Vose we have a standard formatting of the model elements that we find promotes good model housekeeping, and helps us and others orientate themselves around the model.

Note that the Vose Find Function window from ModelRisk is particularly suitable for making your models clear this way: it allows you to find, select and format all spreadsheet cells containing a certain VoseFunction or set of VoseFunctions (e.g. all distributions used in the model).

Outputs

Outputs of your model are the variables that you wish to study. You may have several outputs in the one model; they may be calculations or ModelRisk distribution functions; they may be single cells or cover a range. You may select intermediary calculations as outputs for checking purposes too. You will notice that we colour all of our outputs red for ease of identification.

Inputs

Inputs can be either parameter values that are used in probability distributions or probability distributions themselves. They come from data or expert opinion. Our preference is to have only parameter values as inputs. For example, an expert might offer the opinion that you will sell PERT(300, 400, 600) units of a product (Also see modeling expert opinion). We would treat the three figures as three inputs - instead of one cell with the PERT formula and its parameters - and construct the model to ensure that all three values are visible. We colour all our input parameters blue.

Calculations

Our coloring convention has all calculations in black. You can also add the convention that all distributions are in italic, for example, and all placeholders (values you don't know yet) with a background color that stands out well.

For models that will be distributed to others, offer a key to allow the reader to easily identify these components. Try to keep the key, together will all assumptions and outputs in the first sheet of the workbook. In fact, in general try to keep a model to just one sheet, sometimes with data held in other sheets, because this helps avoid reference errors.

Read on:  Using range names for model clarity

 

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