Help with critical path calculation

[ProjectUser84]

I am using MS Project 2002. I have two tasks: Clean Kitchen; Work: 1
hours; Resource: Tim Clean Bathroom; Work: 16 hours; Resource: Tim Bu
MS Project is showing both tasks starting at the same time, with th
critical path of 16 hours. The tasks show Tim using 100% effort and Ti
is scheduled to work only 8 hours a day. So why does the task finish i
16 hours and not the expected 30 hours (16+14)? Without creating fals
dependencies, how do I make sure that Project properly shows 1) that th
tasks must be done sequentially, or 2) that Tim's 8-hour work day mus
be split between these two tasks? In either case, the critical pat
should show that this project will have a 30-hour duration.

Read more
http://www.justanswer.com/questions/2lya2-using-ms-project-2002-two-tasks#ixzz0SmlpLTA

 

[Jack Dahlgren MVP]

Either create the dependency - is it not false if it is a dependency and
choosing a sequence of work is perfectly valid. Or use resource leveling to
level Tim's tasks.

Both are reasonable solutions.

-Jack Dahlgren

 

[Jim Aksel]

Not exactly. A couple of things. First, do not confuse work with duration.
I can do 2 hours of work in three days of duration. There are columns for
each.

The critical path is calculating correctly at 2 days because the tasks run
in parallel. It is possible for the tasks to be worked concurrently,
although we are overloading Tim to do so. We would only want to establish a
Finish to Start dependency on the tasks if they could not be worked
simultaneously. For example, if the bathroom was a room off the kitchen, it
would make sense to clean the bath first then move on to the kitchen...
perhaps becuase we had to let the floor dry or something. Notice it is the
realationship between the tasks that establishes the dependency, not the fact
that Tim is working both.

What you have is a resource allocation problem, Tim is overloaded. You can
fix that by using Tools/Level Resources... There is more detail about your
options there in the help (on the Resource Leveling form). This algorithm
will assign Tim to work the tasks sequentially.

Under no circumstances does Project reallocate the resource assignmetns
among the tasks. If you assigned Tim at 100% he will stay that way. If you
want the taks to work concurrently and have Tim split his time, you will have
to do that manually. Here is how. In the Gantt view, select Window/Split...
you now have two windows with the work assignments at the bottom. You will
see Tim is allocated at 100%. Change that to 50% and the duration will
doulble. Do the same thing for the other task. Now, Tim works 50% on each
task for twice as long and the length of your critical path changes. If the
two tasks are differing amounts of work (and therefore duration), project
will not automactically increase Tim's allocation to 100% once the first task
is done. If he was assigned at 50% he will stay there. Project is not smart
enough to know you want to keep Tim gainfully employed at 100% if possible.
That would be a nice feature, perhaps in Project 2012...

In your case, the project will show a critical path of a duration that
depends on the resource assignments. If Tim has help from Bob, the duration
will be 2 days. If Tim works solo the duration is (almost) four days if you
level Tim as a resource. If Tim is not leveled, the tasks run in parallel
and the correct critical path duration is two days.

If this post was helpful, please consider rating it.

Jim Aksel, MVP

Check out my blog for more information:
http://www.msprojectblog.com

 

[ProjectUser84]

Thanks Jim,

I had that thought too. Unfortunately, the tasks are not running
concurrently and Tim is not overallocated. For some reason it only
considers the second task critical. When I assign a start date to the
first task, both tasks become critical. This seems like it solves the
problem, right?

Sadly, when I add a third task that only Tim can do, it gets inserted
into the middle of my first two tasks and is not considered critical,
although the first and third task both still are critical. What do you
think that might be all about? It certainly seems to defy any logic I
can think of.

Thanks for all your help.

 

[Jan De Messemaeker]

Hi,

Sorry, how can you say that Tim is not overallocated if he is planned to do
two tasks in parallel, each at 100%? Use Resource leveling to resolve the
overallocation rather than denying it )
Greetings,
--
Jan De Messemaeker
Microsoft Project Most Valuable Professional
+32 495 300 620
For availability check:
http://users.online.be/prom-ade/Calendar.pdf

 

[ProjectUser84]

Jan,

You caught me! I was trying to conceal the fact that Tim is going to
be cleaning the kitchen and the bathroom at the same time! I DIDN'T WANT
ANYONE TO KNOW!

Just kidding!

I know that Tim is not doing both of these tasks at the same time
because I am looking at the Gantt chart and it clearly shows that he is
doing one task, and then doing the other - not both at the same time.

I have used resource leveling. It does not solve the problem.

 

[Jan De Messemaeker]

It may not show the "right" critical path but it does put the tasks in a
feasible order ..

--
Jan De Messemaeker
Microsoft Project Most Valuable Professional
+32 495 300 620
For availability check:
http://users.online.be/prom-ade/Calendar.pdf

 

[Jim Aksel]

You are not being a naughty boy and keying in dates are you?
It seems we've shifted the question. First you were saying Tim works both
concurrently, now he does not but your critical path is still a mess. Sorry,
I am confused.

Might you care to donate the file jeaksel at yahoo dot com
--
If this post was helpful, please consider rating it.

Jim Aksel, MVP

Check out my blog for more information:
http://www.msprojectblog.com