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11.17. Parameter Entry Table versus Risk Categories

Applies to:
@RISK 6.x/7.x, Professional and Industrial Editions

A parameter entry table and a risk category both seem like a way to select a group of tasks and apply variation to them. How do I choose between them?

Choose a parameter entry table when you want to show parameters — such as min, most likely, and max — in dedicated columns for easy editing. Choose a risk category when you want a group of tasks all to vary by the same percentages or same amounts. There can be only one parameter entry table, but there can be multiple categories, with different variation for each category.

With either tool, most people chose to vary the Duration field. But you can choose any numeric or date field.

Creating a parameter entry table gives you dedicated columns for minimum, most likely, and maximum, or other appropriate distribution parameters. You can then edit any of those numbers without having to edit formulas. A project can have only one parameter entry table, so plan for this before you create it. You can have multiple risk categories.

Can I use both in the same project?

Yes, but you should not apply both of them to any of the same tasks.

How do I create a parameter entry table or a set of risk categories?

The two dialogs are similar, so we'll explaine the Parameter Entry Table dialog in detail, and then gloss over the Risk Categories dialog.

Click Project » Model Tools » Parameter Entry Table to open the dialog box.
Choose the field (column) for which you're creating the parameter entry table.
Set your desired type of variation.
Under Build Entry Table For, select All Tasks to apply the table to every task in the project, or Selected Tasks to apply the table to just e tasks that meet some criterion. Either setting will automatically ignore milestones and summary tasks, which cannot have distributions.
If you chose Selected Tasks, Click Add if you want to choose tasks by clicking, or Add Marked if you want to choose them based on some characteristic. For example, if you chose Add Marked and then click in a Duration field with a value of 1 day, @RISK will select every task that has a Duration of 1 day; if you click on a text field that has the value Construction, @RISK will select every task that has the value Construction in that same column. (This includes any tasks that are invisible because of filtering.)
If you plan to have project managers update the MPP file, check (tick) the box Also Add Entry Table to MPP. If everyone who will be updating the project has @RISK, there's no need to duplicate the parameter entry table in the MPP file.

Risk categories are a similar idea to the parameter entry table, but you can designate different categories with different distribution functions. You select distributions the same way as for a parameter entry table, and you select tasks using Add or Add Marked in the same way, but @RISK writes your chosen variation directly into the field you selected, for every selected task. For example, if you selected Duration to vary between 5% below base and 20% above base, @RISK will write RiskVary functions with those numbers into the Duration field of the tasks you selected. You can create additional categories when you want, or change the variation method of an existing category.

Risk categories and parameter entry tables are similar, but they do have a few differences. Here's a summary:

	Risk Categories	Parameter Entry Table
Number allowed	Multiple	Only one
Same distribution?	Yes, within one category; can be different for different categories	Yes
Same parameters?	Yes, within one category; can be different for different categories	Easily edit the parameters individually
Parameters visible in reserved columns in worksheet?	No	Yes

Last edited: 2016-09-21

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