Redistribution of effort on adding new resource

[Amit]

Hi All,

Please help me in understanding the calculation done by Project when a
new resource is assigned to a task. Following is the scenario...

i create a new task (Fixed unit - effort driven) with duration 9 days
and assign two resources r1 and r2 with units 115% and 85%. Project
calculates the duration as 9 days with individual effort as 82.8 and
61.2 hrs respectively. This comes as expected.

Now, if i change the unit for the resource r1 from 115% to 100%, the
individual efforts (and total effort) remain fixed but the duration of
the task changes to 10.35 days with r1 becoming the driving resource.

Now, if i add a third resource r3 to the task with units 90%, the
duration of the task changes to 6.82 days and individual efforts change
to 54.57, 40.33 and 49.1 hrs respectively for r1, r2 and r3.

These individual efforts donot satify the formula

(Individual Assignment)/(Total Assignment) * Total Effort

This is because of the intermediate step of reducing the units which
caused change only in duration and not the individual effort.

How is the Project calculating these individual efforts and the new
duration in the last step?

Thanks,
Amit

 

[davegb]

Hi All,

Please help me in understanding the calculation done by Project when a
new resource is assigned to a task. Following is the scenario...

i create a new task (Fixed unit - effort driven) with duration 9 days
and assign two resources r1 and r2 with units 115% and 85%. Project
calculates the duration as 9 days with individual effort as 82.8 and
61.2 hrs respectively. This comes as expected.

Now, if i change the unit for the resource r1 from 115% to 100%, the
individual efforts (and total effort) remain fixed but the duration of
the task changes to 10.35 days with r1 becoming the driving resource.

Now, if i add a third resource r3 to the task with units 90%, the
duration of the task changes to 6.82 days and individual efforts change
to 54.57, 40.33 and 49.1 hrs respectively for r1, r2 and r3.

These individual efforts donot satify the formula

(Individual Assignment)/(Total Assignment) * Total Effort

This is because of the intermediate step of reducing the units which
caused change only in duration and not the individual effort.

How is the Project calculating these individual efforts and the new
duration in the last step?

Thanks,
Amit

I don't have Project on this computer where I am, but I don't see
anything wrong with what you say happened. Project did as expected. I'm
not sure what you expect, since what you wrote isn't a formula. To be a
formula, it needs an equals sign.
The standard formula for Project is
Work = Duration x Units
if Duration and work are in the same units (days, hours, min, etc). If
they are in different units, there needs to be a correction factor in
the equation. If Duration is in days, and work is in hours (defaults),
the formula becomes
Work = Duration x units x8

When you're in fixed Units, and you change units, duration will change
to try to maintain balance. And when you add another resource on an
effort driven task, it will take on some of the work assigned to the
resources already working on the task, thus reducing the duration.
That's exactly how Project works!

 

[Amit]

Thanks Dave.

I just wanted to know how Project redistributes work when a new
resource is added in the third step.
Any idea??

Regards,
Amit

 

[davegb]

Thanks Dave.

I just wanted to know how Project redistributes work when a new
resource is added in the third step.
Any idea??

Regards,
Amit

To come up with a formula, I'd have to do a series of these types of
events, then figure out how project is doing the calculation. But when
I first looked at the numbers, without having Project available, it
looked reasonable because when you added the third resource, the work
of the other 2 decreased in "reasonable proportion", as did the
duration (roughly a third). Which is what I expect with an effort
driven task.
How project handles these things doesn't always make sense to many of
us. But once you understand what it does, it's usually fairly
predictable, given you know the "rules" by which it operates.
Hope this helps in your world.

 

[Mike Glen]

Hi Amit,

Welcome to this Microsoft Project newsgroup

You might like to have a look at my series on Microsoft Project in the
TechTrax ezine, particularly #10 - Multiple Resource Assignments, at this
site: http://tinyurl.com/2xbhc or this:
http://pubs.logicalexpressions.com/Pub0009/LPMFrame.asp?CMD=ArticleSearch&AUTH=23
(Perhaps you'd care to rate the article before leaving the site,
Thanks.)

FAQs, companion products and other useful Project information can be seen at
this web address: <http://www.mvps.org/project/>

Hope this helps - please let us know how you get on

Mike Glen
MS Project MVP

 

[Amit]

Thanks a lot, Dave.

Thanks Mike.
I did go through your articles and those really helped me a lot. ( I
did care to rate them as well )
However, i am specifically looking for the way calculation is done by
Project in the case described by me in my first post.
Hopefully, i will be able to convert my understanding into formulas.

Regards,
Amit

 

[Mike Glen]

You're welcome, Amit. I hope you can find what you're looking for. If you
do - please consider posting your findings here for the benefit of us all.


Mike Glen
MS Project MVP