Elapsed duration & Fixed duration tasks

[Mary Ann]

I am using Project 98

I am trying to get my head round elapsed duration tasks. I understand that
with an elapsed duration task it is scheduled irrespective of the work
calendar, so e.g. a 5 day elapsed duration task would constitute 120 hours
work (5 x 24) and could be scheduled over a non-working weekend.

I have read that an elapsed duration task is automatically defined as fixed
duration. When I add / remove resources, the task duration and the task work
remain unaltered. It does therefore seem to act like a Fixed Duration,
Effort Driven task. But when I look at the Task Information it is shown as
Fixed Units, Effort Driven – is this a bug or am I missing something?

 

[Steve House [MVP]]

Not a bug that I know of - there are many times where Project has a behavior
different from what the task labels say. For example, split the screen so
you can see the complete picture in the bottom pane and assign a resource
100% to a 5 day task with the task type as fixed effort. After assigning
you'll see the work is 40 hours. Now change his assignment to 50% and click
the ok button. The work stays at 40 hours and the duration changes to 10
days. In other words, it behaves as if it was fixed work even though it's
actually listed as fixed effort. I advocate using the split screen for
making and editing resource assignments in all except the simplest
situations because it gives you fingertip access to all of the variables and
settings so you can see exactly what's going on.

I'd suggest beinghhhbhb very cautious about how you use elapsed duration
tasks. They have their uses - automated processes that can run without
regard to working hours or a human resource being physically present the
whole time, for example. But taking your example - making that task elapsed
duration and assigning a resource 100% means that the resource is going to
do 120 hours of work in one continuous stretch - no meal breaks, no sleep
periods, no rest or down time of any sort at all. People simply can't work
like that.

 

[davegb]

Steve,
I read and agree with your comments, but I'm not sure what you mean by
"fixed" effort task? Do you mean "Effort Driven". At first, I thought
you meant "fixed work", but then you say it acts as if it's fixed work,
so that can't be it. Please elaborate on "fixed effort".
Thanks.

 

[Steve House [MVP]]

Fixed effort means the resource assignment percentage is the factor held
constant. In the equation W=D*E you can arbitrarily hold any chosen term
constant, edit a second term, and Project will calculate the third for you.
Fixed Work designates W, fixed duration sets D, and fixed effort specifys E
to be the constant term. Task type governs when editing existing resource
assignments. If I've got one guy painting a room assigned 100% and taking 5
days, that's 40 hours of work. If I change his assignment to 50% , either
the WORK should recalculate to 20 man-hours (fixed duration) or the DURATION
should recalculate to 10 days (fixed work). If it's fixed effort it means
he's still expected to work 100% for the full span of the task and then I
can change the work and the duration gets recalculated or I can change the
duration and the work gets recalculated. By the way, the reason why "fixed
effort" is the out-of-the-box default setting is that 90% of the time when
you're fine tuning a pal you're either revising the work estimate or the
duration estimate while still expecting the resource to devote his full
attention to the tasks he's been assigned. But it's up to me to know just
what I intend to happen in the edit and thus which task type to set before
editing the assignment.

That's something completely separate from effort driven considerations. The
effort driven setting refers to what happens when you add or remove bodies
from the task. If I'm painting a room with one painter and then I add a
second painter, the duration drops because each of them does part of the
work and we get it done quicker. That's effort driven behavior. On the
other hand if I'm holding a meeting with several people booked and I add
another person to attend, the length of the meeting doesn't change -
non-effort driven behavior.

 

[JackD]

Easy to be confused. Project calls it "Fixed Units" implying the number of
resource units is fixed.

One easy way to avoid confusion is to be aware of the units.

Remember Duration x Units = Work

Duration has as a unit things such as hours, days, weeks.
Work has the units of person hours, machine days or other such things.
So Units (or as Steve claims "Effort") should have as it's units people or
machines or other types of resources.

Because of this I think Steve should rethink his terminology for the future.
No one really thinks of a person as measure of effort. It also explains why
Microsoft uses such an awkward term.

 

[Steve House [MVP]]

I agree with you, we should be more consistent. Consider how many messages
and references quote the basic work formula as being W=D*E, not W=D*U. I
confess I refer to the resource assignment level term of the equation as
"effort" by habit of many years standing but now that you mentioned it, it
really could be more precise if I called it "units." mea culpa

Actually some sources do equate units == effort because especially when
expressed as a percentage, it represents what portion of their potential
output over a period of time that they are actually producing. If over the
course of an 8-hour workday Joe produces the amount of deliverable he
*could* have done in 4 hours, his level of effort is 50% of what he would
being doing if he went at it full-tilt. He's working at a 50% unit level of
effort. And I have seen many, many instances where "fixed effort" and
"fixed units" are used interchangeably.

This usage of the word is also conceptually consistent with the meaning of
the terms effort driven and non-effort driven. When I add a person - an
additional unit - to a task and the duration shortens, it is responding to
the increased effort, i.e., number of units, that is being applied to the
task.

Making it even more interesting <g>, some sources use effort == work and
express our 1st Axiom as E=DU.

IMO "units" is more accurate terminology when you are using integer values
to represent people - 1 unit meaning one person, 2 units 2 people, etc -
while "effort" is more accurate when referring to the level of commitment
expected from a single resource.


--
Steve House [MVP]
MS Project Trainer/Consultant
Visit http://www.mvps.org/project/faqs.htm for the FAQs

 

[JackD]

I don't disagree that effort is correct. It is. But it is confusing. That is
all.

 

[davegb]

Thanks for the clarification!