Estimating the duration uncertainty and probability of tasks using code libraries

Estimating the duration uncertainty and probability of tasks using code libraries, by assigning codes from risk analysis code libraries to tasks, gives you slightly less control than estimating duration uncertainty and probability against individual tasks, but enables you to estimate duration uncertainty and probability against a selection of tasks in much less time. If you normally think of risk in terms of minimum and maximum percentages, this method of recording risk will probably suit you.

As you can use a combination of duration uncertainty and probability estimation methods, you may want to estimate duration uncertainty and probability against certain key individual tasks and use code libraries, or default percentages, to estimate duration uncertainty and probability against less key tasks.

To estimate duration uncertainty and task probability using code libraries, you must first create a risk analysis code library within Asta Powerproject, containing codes that define the minimum and maximum duration values, and optionally the task probability, in terms of percentages. You can then assign the codes to tasks to estimate the duration uncertainty and probability of the tasks. Alternatively, you can amend existing code libraries that have already been assigned to tasks.

Creating risk analysis codes

You can call the code library that you create for use in risk analysis anything you like, but the names of the codes within the library must follow a precise syntax, as the values are extracted from the names of the codes.

Note the following points about the code names:

Each code name must contain two valid percentages, the first representing the minimum duration value and the second representing the maximum duration value.
The first percentage must be lower than the second.
Each code name can optionally contain a third percentage, representing the task probability.
If the code names do not include a third percentage, the task probability is assumed to be 100%.
The code names can include other characters.
When thinking in terms of minimum duration and maximum duration percentages, 100% corresponds to the current duration of each task.

Some examples of valid risk analysis code names are displayed below:

Code name	Description
90% 110%	Minimum duration = 90%. Maximum duration = 110%. Task probability assumed to be 100%.
Min risk 60% max risk 140%	Minimum duration = 60%. Maximum duration = 140%. Task probability assumed to be 100%.
80% 120% 50%	Minimum duration = 80%. Maximum duration = 120%. Task probability = 50%.
Low 85% High 115% Occurs 75%	Minimum duration = 85%. Maximum duration = 115%. Task probability = 75%.

If you want to, you can create more than one risk analysis code library. When you carry out risk analysis, you can select the code library that you want to use to determine risk.

Alternatively, you can amend existing code libraries that have already been assigned to tasks by editing their names and adding risk percentages to them. For example, if you have a code library of names showing who is responsible for a task, you could add percentages to each name depending on how reliable you think that person is (you could rename a code called Harriet Wheeler to Harriet Wheeler 90% 110%). This enables you to get up to speed with Risk Analysis very quickly.

To create a risk analysis code library and codes:

On the View tab, in the Show group, click Library Explorer.
Select Code Library from the tree view. A list of code libraries appears in the list view.
Right-click a blank area of the list view and select New Code Library. A new code library appears in the list view, with the cursor flashing in the Name column.
Enter a suitable name for the code library, for example Risk Analysis, then click a blank area of the list view to finish editing.
Right-click the new code library folder in the list view and select New Code Library Entry. The folder opens and a new code is created within it, with the cursor flashing in the Name column.
Enter a name for the code library entry, following the syntax specified above, then click a blank area of the list view to finish editing.
Specify an appearance for the code.
Create more codes within the code library to represent the full spread of uncertainty. For example, you could create three codes, called Low Risk, Medium Risk and High Risk, each with appropriate percentages.

You can now assign the codes to tasks.

Assigning risk analysis codes to tasks

Once you have created risk analysis codes, you can assign them to tasks within the current project. You can assign codes to single tasks, or to more than one task at the same time by selecting multiple tasks.

If you assign a code to a summary task or expanded task, the duration uncertainty percentages apply to all tasks within the summary group or subchart that do not have risk values associated with them at the task level. This saves you time in assigning codes.

To assign risk analysis codes to tasks:

Select the task(s) to which you want to assign a risk analysis code.
Locate and open the risk analysis code library in the project view.
Click and drag the appropriate risk analysis code from the project view to one of the selected tasks and release the mouse button when the mouse pointer is located over one of the selected tasks.