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edited for brevity and added fixed-unit and fixed-work examples inspired by other answers

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edited May 23, 2014 at 17:07

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Okay, I'm going to give this a shot for fixed-duration tasks, which I think I have an example of. I'm hoping it provides a tangible example of what I'm looking for and encourages others to write their own better answers.

Fixed-duration tasks have the following attributes:

When the duration is increased units are constant and work is recalculated

When work is increased duration is fixed and units are increased

When units are increased the work per resource decreases

and vice versa for changes in the opposite directions

A good example of a fixed-duration type task is: Program Management Level-of-Effort.

Since an LOE activity is not itselfNot a work item directly associated with accomplishing the final project product, service or result, but rather one that supports such work,it; its duration is based on the duration of the discrete work activity it is supporting — oiling machinery will start when manufacturing starts and finish when it finishes.

LOE tasks are a good example of an appropriateBecause duration is fixed-duration task because:

If the project duration changes the duration of supporting LOE should change with it. Assuming the effort required for status and coordination remains unchanged it's appropriate to assume the unitsmore (i.e. staffing) is constant and the workunits (integral of units over time) changes accordinglyi.

If the amount of effort required to manage the program changes (e.g. the customer is more needy than anticipatedproject managers) and more units are assigned to PM functions to keep up, then it makes sense for the work to increase:means more people are supporting for the same duration of timehours spent managing.
If more people are added to the task to perform the same amount of work then each unit's allocation to the task decreases because thereless work means less units are more people performing the same effort over the same fixed time spanrequired.

I've got nothing forIncreasing duration means the other two task typesmanagement supports the project longer and thus does more work. Hence

For fixed-unit and fixed-work tasks revising either units or work changes the questionduration. They differ in what's recalculated when duration is changed.

Fixed-unit example: writing a report where the depth of the analysis is flexible.

Paul's analysis skills are so specialized only he can write Report X. If the duration changes then the scope of the report (i.e. the work) changes with it so he can finish on time.

Fixed-work example: painting a fence.

How long we have to paint the fence determines how many people need to work on it. Less time means a larger crew of painters.

Fixed-duration tasks have the following attributes:

When the duration is increased units are constant and work is recalculated

When work is increased duration is fixed and units are increased

When units are increased the work per resource decreases

and vice versa for changes in the opposite directions

A good example of a fixed-duration type task is Program Management Level-of-Effort.

Since an LOE activity is not itself a work item directly associated with accomplishing the final project product, service or result, but rather one that supports such work, its duration is based on the duration of the discrete work activity it is supporting — oiling machinery will start when manufacturing starts and finish when it finishes.

LOE tasks are a good example of an appropriate fixed-duration task because

If the project duration changes the duration of supporting LOE should change with it. Assuming the effort required for status and coordination remains unchanged it's appropriate to assume the units (i.e. staffing) is constant and the work (integral of units over time) changes accordingly.

If the amount of effort required to manage the program changes (e.g. the customer is more needy than anticipated) and more units are assigned to PM functions to keep up, then it makes sense for the work to increase: more people are supporting for the same duration of time.
If more people are added to the task to perform the same amount of work then each unit's allocation to the task decreases because there are more people performing the same effort over the same fixed time span.

I've got nothing for the other two task types. Hence the question.

Fixed-duration example: Program Management Level-of-Effort

Not a work item directly associated with the project product but one that supports it; its duration is based on the duration of the activity it is supporting.

Because duration is fixed:

more units (i.e. more project managers) means more hours spent managing.
less work means less units are required.

Increasing duration means the management supports the project longer and thus does more work.

For fixed-unit and fixed-work tasks revising either units or work changes the duration. They differ in what's recalculated when duration is changed.

Fixed-unit example: writing a report where the depth of the analysis is flexible.

Paul's analysis skills are so specialized only he can write Report X. If the duration changes then the scope of the report (i.e. the work) changes with it so he can finish on time.

Fixed-work example: painting a fence.

How long we have to paint the fence determines how many people need to work on it. Less time means a larger crew of painters.

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created Dec 18, 2013 at 5:45

Adam Wuerl

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Fixed-duration tasks have the following attributes:

When the duration is increased units are constant and work is recalculated
When work is increased duration is fixed and units are increased
When units are increased the work per resource decreases
and vice versa for changes in the opposite directions

A good example of a fixed-duration type task is Program Management Level-of-Effort.

Since an LOE activity is not itself a work item directly associated with accomplishing the final project product, service or result, but rather one that supports such work, its duration is based on the duration of the discrete work activity it is supporting — oiling machinery will start when manufacturing starts and finish when it finishes.

LOE tasks are a good example of an appropriate fixed-duration task because

If the project duration changes the duration of supporting LOE should change with it. Assuming the effort required for status and coordination remains unchanged it's appropriate to assume the units (i.e. staffing) is constant and the work (integral of units over time) changes accordingly.
If the amount of effort required to manage the program changes (e.g. the customer is more needy than anticipated) and more units are assigned to PM functions to keep up, then it makes sense for the work to increase: more people are supporting for the same duration of time.
If more people are added to the task to perform the same amount of work then each unit's allocation to the task decreases because there are more people performing the same effort over the same fixed time span.

I've got nothing for the other two task types. Hence the question.