Risk-Activity Impacts


Words on this page that have been underlined and italicized can be found in the glossary on the right-hand side of the page.

Tip

When a risk's schedule impact occurs, an activity's duration is extended by the specified impact. If, on the other hand, the risk results in a delay, this situation can be better modeled via Existence Risks or Floating.

Inherited Assignments

In NetRisk, quantitative probability and impact may be entered at the risk/scenario-level in the risk register.

  • This saves time, as the probability and impact are inherited automatically and do not need to be entered one-by-one

  • Subsequent modifications to the probability or impact are automatically carried down to each assignment

An inherited assignment is identified by an icon next to each value that has been inherited.

  1. Click the Risk  driver.

  2. Click the View button above the top list and choose Risk Register.

  3. Select the desired risk or scenario in the upper list.

  4. Enter a value in the Probability (Quantitative) column.

  5. In the Distribution Type column for schedule and/or cost, click to choose a desired distribution type.

  6. Enter a value in each of the required columns.

    Required columns will display a Warning  icon. If none of the required columns are visible, they must be turned on (see Customizing Columns). So long as any column contains a warning, the entire row will be colored orange (for a risk/scenario with no inherited assignments) or red (for a risk/scenario with inherited assignments).

  7. In the lower list, next to the desired activity(s), check the box in the Schedule column to assign a schedule impact and next to the Cost column to assign a cost impact.

Tip

To force all activity assignments to the top, click the Sort icon, uncheck Organize by WBS, click Assign twice until the down arrow shows up next to it (descending order), and then make sure the list is then scrolled all the way to the top.

Un-inheriting Risks/Scenarios

If an inherited risk assignment has any value modified at the activity level, any modifications to the probability or impact in the register will no longer be carried down to each assignment.


Individual vs. Grouped Assignments

By default, all assignments underneath a given risk with the same probability of occurrence will be impacted in the same iterations as each other as a group. To impact activities individually, uncheck the box in the Correlate Probability column in the lower list. If the column isn't visible, it must be turned on first (see Customizing Columns). For more on individual vs. group assignments, see the Risks section in The Risk Register.

Removing an Assignment

An assignment can be removed from the selected scenario or from all scenarios underneath the same risk - the choice is made when unchecking the box.

  1. Click the Risk  driver.

  2. Click the View button above the top list and choose Risk Register.

  3. Select the desired risk or scenario in the upper list.

  4. In the lower list, next to the desired activity(s), uncheck the box in the Schedule column to remove schedule impact or in the Cost column to remove cost impact.


Activity View

Whereas the Risk Register view is useful for assigning activities to designated risks, the All Activities view is useful for assigning risks to designated activities.

  1. Click the Risk  driver.

  2. Click the View button above the top list and choose All Activities.

  3. Select the desired activity in the upper list.

  4. In the lower list, check the box next to the desired risk in the Schedule column or Cost column accordingly.


In the activity view, risks cannot be created or modified.

Sampling In Parallel vs. In Series

By default, all risk schedule impacts are sampled in parallel. This can be set individually for each risk impact by clicking the dropdown in the Sampling Order column and choosing between In Series and In Parallel.

OptionDefinition
In ParallelLargest impact taken
In SeriesAll impacts added together

Probabilistic Branching

Two basic basic probabilistic branching scenarios can be modeled in NetRisk. Both methods require creating and linking 0-day activities in your schedule file (task dependents in P6 or delays in NetPoint). Once in NetRisk, follow the instructions above to create one risk for each activity where the schedule impact entered on the risk will represent the duration (since the determinstic duration is 0).

ScenarioDescriptionProcess
AA chain of activities all occur, or neither occursEnter the same probability for each risk and then correlate the existence of each risk to the first risk with a coefficient of 1.
BEither one activity occurs or another activity occursEnter unique probabilities for each risk which add up to 100% and then correlate the existence of the second risk to the first risk with a coefficient of -1.

For more info on correlations, see Risk-to-Risk Existence Correlations.

Choosing Distribution Types

Choosing a distribution type should be determined by the level of confidence in the values being chosen. When entering the range, the minimum is interpreted as the optimistic estimate, or best case scenario; the most likely is interpreted to be the most likely estimate; and the maximum is interpreted as the pessimistic, or worst case scenario. 

Distribution TypeWhen to Use...
Constant
  • Use if there is no possible range, but rather only one possible value
Beta-Pert
  • Smoother than a triangular
  • Use if you are fairly confident in your estimate for the most likely but want to control how confident you are in the extremes
  • To use Modified Beta, set lambda to any value other than 4 (default)
  • If you set lambda to 0, the probability of the extremes will be lower than with, for example, a Triangular distribution
Log-Normal
  • Use if you know the duration is the product of several other variables
  • For example, many natural biological events can be modeled logarithmically, as can many variables in economics and finance
Normal
  • Use if the minimum estimate is just as likely to occur as the maximum estimate
  • Not recommended for durations, since an activity will be delayed more often than completed early
  • More typical with risk impacts
Triangular
  • Use if your confidence in the most likely is neither high nor low, as the probability of the extremes will be higher than a Beta-Pert but lower than a Uniform
Trigen
  • Use if what's been entered for the minimum and maximum may actually be too conservative, or if the minimum and maximum may not be the absolute minimum and maximum possible
  • Values below the Low % and above the High % will not be sampled
Uniform
  • Use if your confidence in the range is fairly low, as the probability will be the same for all possible values.
  • Not recommended for durations, since an activity will be delayed more often than completed early

Copy/Paste/Fill Down

Once entered, probability and impact ranges can be copied and pasted or filled down to save time. For details, see Interface Tour.

Available Table Columns

For details on customizing columns, filtering, sorting, and organizing by WBS, see Interface Tour.


 Quantitative Risk Columns...
ColumnDescription
Activity AssignmentsA summary of all activities assigned by ID. If no user-defined ID exists, the internal ID is shown.
Cost BehaviorA toggle for controlling whether the risk cost impact will be treated as time-dependent or time independent. Time-dependent cost impacts include costs such as labor and equipment rented by the day and will adjust with the activity duration. These inputs should be entered as a rate ($ per day). Time independent cost impacts include costs such as materials or overhead and will not adjust with the activity duration. These costs should be entered as a total.
Cost Distribution TypeA shape for organizing a range of cost impact values.
Cost High %A range value used when Trigen is chosen for the cost impact distribution type.
Cost LambdaA range value used when BetaPert is chosen for the cost impact distribution type.
Cost Low %A range value used when Trigen is chosen for the cost impact distribution type.
Cost MaxA range value used for the following cost impact distribution types: BetaPert, Triangular, Trigen, and Uniform.
Cost MeanA range value used for the following cost impact distribution types: Normal and Log-Normal.
Cost MinA range value used for the following cost impact distribution types: BetaPert, Triangular, Trigen, and Uniform.
Cost Most LikelyA range value used for the following cost impact distribution types: Constant, BetaPert, Triangular, Trigen, and Uniform.
Cost Std.Dev.A range value used for the following cost impact distribution types: Normal and Log-Normal.
Probability (Quantitative)

The percentage of iterations that the risk will be sampled as occurring.

This field (as long as it were empty) will default to the midpoint of the range from the Qualitative Thresholds window. For example, if a risk is set to M (40-60), then this field would be pre-filled to 50. Subsequently changing the risk to an H, however, or modifying the values in the Qualitative Thresholds window will have no effect.

Schedule Distribution TypeA shape for organizing a range of schedule impact values.
Schedule High %A range value used when Trigen is chosen for the schedule impact distribution type.
Schedule LambdaA range value used when BetaPert is chosen for the schedule impact distribution type.
Schedule Low %A range value used when Trigen is chosen for the schedule impact distribution type.
Schedule MaxA range value used for the following schedule impact distribution types: BetaPert, Triangular, Trigen, and Uniform.
Schedule MeanA range value used for the following schedule impact distribution types: Normal and Log-Normal.
Schedule MinA range value used for the following schedule impact distribution types: BetaPert, Triangular, Trigen, and Uniform.
Schedule Most LikelyA range value used for the following schedule impact distribution types: Constant, BetaPert, Triangular, Trigen, and Uniform.
Schedule Sampling OrderA toggle for sampling risk schedule impact in series or in parallel. When sampling In Series, if there are multiple risks impacting the same activity, all the impacts are added together. When sampling In Parallel, if there are multiple risks impacting the same activity, only the largest impact is taken.
Schedule Sampling ValuesA summary for displaying the schedule impact distribution type plus any range inputs together in the same field.
Schedule Std.Dev.A range value used for the following schedule impact distribution types: Normal and Log-Normal.
Schedule UnitA toggle for ranging risk schedule impact in Days or % Variance.

For qualitative columns, see The Risk Register.

 Activity Assignment Columns...
ColumnDescription

Abbr. Description

A NetPoint-unique field limited to 48 characters for describing the activity.

Calendar

The schedule that work on the activity can take place.
Codes

A submenu containing one column for every code in the schedule.

The organization and visibility of code columns is NOT saved with the application. Code columns must be turned back on every time the tab is changed.

Completed DurationThe amount of time already completed.

Constraint #1

The primary constraint, if any. The following abbreviations are used: ALAP (As Late As Possible), MEO (Finish On), MEOA (Finish On Or After), FNL (Finish On Or Before), MS (Mandatory Start), MF (Mandatory Finish), MSO (Start On), SNE (Start On Or After), and MEOB (Start On Or Before).

Constraint #2

The secondary constraint, if any. The following abbreviations are used: ALAP (As Late As Possible), MEO (Finish On), MEOA (Finish On Or After), FNL (Finish On Or Before), MS (Mandatory Start), MF (Mandatory Finish), MSO (Start On), SNE (Start On Or After), and MEOB (Start On Or Before).
Constraint Behavior

A toggle for controlling how constraints behaves during simulation (only enabled if an activity/milestone has a constraint).

If an activity has two constraints and Maintain is chosen, both will be maintained unless one is triggered, in which case the second one will be ignored.

ALAP constraints will never be maintained and this option disabled for activities with only ALAP constraints (if an ALAP and another constraint exist and Maintain is chosen, only the other constraint will be maintained).

Correlate ProbabilityA toggle for determining whether or not the assignment will be correlated. If checked, the sampling of the occurrence of the risk will be sampled in the same iterations as any other assignment with the same probability value.
Cost

A checkbox for assigning the risk's cost impact.

This column cannot be removed from the table.

Cost BehaviorA toggle for controlling whether the risk cost impact will be treated as time-dependent or time independent. Time-dependent cost impacts include costs such as labor and equipment rented by the day and will adjust with the activity duration. These inputs should be entered as a rate ($ per day). Time independent cost impacts include costs such as materials or overhead and will not adjust with the activity duration. These costs should be entered as a total.
Cost Distribution TypeA shape for organizing a range of cost impact values.
Cost High %A range value used when Trigen is chosen for the cost impact distribution type.
Cost LambdaA range value used when BetaPert is chosen for the cost impact distribution type.
Cost Low %A range value used when Trigen is chosen for the cost impact distribution type.
Cost MaxA range value used for the following cost impact distribution types: BetaPert, Triangular, Trigen, and Uniform.
Cost MeanA range value used for the following cost impact distribution types: Normal and Log-Normal.
Cost MinA range value used for the following cost impact distribution types: BetaPert, Triangular, Trigen, and Uniform.
Cost Most LikelyA range value used for the following cost impact distribution types: Constant, BetaPert, Triangular, Trigen, and Uniform.
Cost Std.Dev.A range value used for the following cost impact distribution types: Normal and Log-Normal.

Description

The text field for describing the activity.

This column cannot be removed from the table when organized by WBS.

Drift

The amount of the time an activity may advance before advancing the project start.
Duration CorrelationsA summary of activities that have been correlated by ID with the coefficient showing in parenthesis.
Early FinishThe date the activity completes when its drift is equal to zero.
Early StartThe date the activity begins when its drift is equal to zero.

Finish Date

The date the activity completes. If actualized, the date is appended with an asterisk ( * ).
FloatThe amount of the time an activity may be delayed before delaying the project completion.
IDThe user-entered unique identifier.
LambdaA range value used when BetaPert is chosen for the distribution type.
Late FinishThe date the activity completes when its float is equal to zero.
Late StartThe date the activity begins when its float is equal to zero.

Planned Duration

The amount of time the activity takes to complete.
Probability (Quantitative)The percentage of iterations that the risk will be sampled as occurring.
Remaining DurationThe total duration minus the amount of time already completed.
Resource CostThe total cost of the activity, as calculated by resource assignments.
Risk AssignmentsA summary of all risks and/or scenarios assigned by ID.
Schedule

A checkbox for assigning the risk's schedule impact.

This column cannot be removed from the table.

Schedule Distribution TypeA shape for organizing a range of schedule impact values.
Schedule High %A range value used when Trigen is chosen for the schedule impact distribution type.
Schedule LambdaA range value used when BetaPert is chosen for the schedule impact distribution type.
Schedule Low %A range value used when Trigen is chosen for the schedule impact distribution type.
Schedule MaxA range value used for the following schedule impact distribution types: BetaPert, Triangular, Trigen, and Uniform.
Schedule MeanA range value used for the following schedule impact distribution types: Normal and Log-Normal.
Schedule MinA range value used for the following schedule impact distribution types: BetaPert, Triangular, Trigen, and Uniform.
Schedule Most LikelyA range value used for the following schedule impact distribution types: Constant, BetaPert, Triangular, Trigen, and Uniform.
Schedule Sampling OrderA toggle for sampling risk schedule impact in series or in parallel. When sampling In Series, if there are multiple risks impacting the same activity, all the impacts are added together. When sampling In Parallel, if there are multiple risks impacting the same activity, only the largest impact is taken.
Schedule Sampling ValuesA summary for displaying the schedule impact distribution type plus any range inputs together in the same field.
Schedule Std.Dev.A range value used for the following schedule impact distribution types: Normal and Log-Normal.
Schedule UnitA toggle for ranging risk schedule impact in Days or % Variance.
Start DateThe date the activity begins. If actualized, the date is appended with an asterisk ( * ).
Total FloatThe float + drift.
TypeThe type of object, e.g. activity, milestone, hammock, etc.
WBS SequenceA value for sorting when organized by WBS.
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 Glossary

Distribution Type: a shape for organizing a range of outcomes (e.g. durations, impacts, etc.).

Impact: the degree to which the risk could affect activity durations.

Probability: the percentage of iterations the risk will be sampled as occurring.