Project 2003 Critical Path

[Racman5487]

Hi I am creating a project in 2003 and have used the wizard to show my
critical path, but the path it has chosen is a single task and quite
obviously not the critical path. I have checked that the task bars colours
are as I thought. Could you please advise as to what may be the problem.
cheers

 

[JulieS]

Hi Caroline,

Are there constraints on the tasks? Have you created predecessors and
successors (links)?

Hope this helps. Let us know how you get along.
Julie

 

[Racman5487]

Hi Julie
Yes there are constraints and predecessors, successors etc but I can't see
where these are preventing the critical path from showing correctly.

Caroline

 

[davegb]

Hi Julie
Yes there are constraints and predecessors, successors etc but I can't see
where these are preventing the critical path from showing correctly.

Caroline

It's a common misconception that "having links" will result in a
critical path. Not so. It will usually result in something showing as
critical, but not a true critical path. To get a correct, meaningful
critical path, you need SCHEDULE CONTINUITY. That is, every working
task has both at least one predecessor and succesor. The only
exceptions are the Start and Finish milestones you need to create to
anchor the schedule at each end and insure schedule continuity, and any
regularly scheduled meetings (usually represented as recurring tasks in
Project). Working tasks being the lowest level tasks in that part of
the outine, those with no subtasks. Summary tasks should not be linked,
partly because they can interfere with schedule continuity.
Schedule continuity is most easily seen by viewing the Network Diagram,
with the link type set to "direct", so it's clear what is linked and
what is not. If there are working tasks that have no predecessors
and/or not successors, you need to figure out what those dependencies
are. A task with no predecessors is a task that can start on day one of
the project, needs no input that is not already available. The Start
milestone is it's only predecessor. A task with no successors is a
task that is done at the end of the project, and has no other task that
needs it's output. The Finish milestone is it's only successor.
Improper use of Constrainst can also cause your CP to "dissappear".
I'll leave that to another thread.

Hope this helps in your world.

 

[JulieS]

Hi Caroline,

Project has calculated the critical path by calculating early start, early
finish, late start and late finish and then calculating slack. Constraints
change the calculation of those dates.

For example:
If I create a project beginning 5 December 2005 and add three one-day tasks
(A, B, C) and link Finish to Start:

Task A Start 5 Dec 05 Finish 5 Dec 05 Late Start 5 Dec 05 Late
Finish 5 Dec 05 Total Slack: 0
Task B Start 6 Dec 06 Finish 6 Dec 05 Late Start 6 Dec 05 Late
Finish 6 Dec 05 Total Slack 0
Task C Start 7 Dec 05 Finish 7 Dec 05 Late Start 7 Dec 05 Late
Finish 7 Dec 05 Total Slack 0

Because all tasks have a total slack of zero, all tasks are on the critical
path.

If I add a Finish No Later Than constraint to Task C with a constraint date
of 8 Dec 05, *no* task is now on the critical path.

Task A Start 5 Dec 05 Finish 5 Dec 05 Late Start 6 Dec 05 Late
Finish 6 Dec 05 Total Slack: 1 day
Task B Start 6 Dec 06 Finish 6 Dec 05 Late Start 7 Dec 05 Late
Finish 7 Dec 05 Total Slack 1 day
Task C Start 7 Dec 05 Finish 7 Dec 05 Late Start 8 Dec 05 Late
Finish 8 Dec 05 Total Slack 1 day

Because of the Finish No Later than constraint, the Late Finish date now
equals the constraint date for Task C. This in turn effects the Late Finish
and Late Start for Tasks B and A.

For more in-depth information on the calculation of critical path see:
http://project.mvps.org/networkanalysis.htm

Mike Glen (fellow MVP) does a terrific job explaining the details of how
slack is calculated.

I hope this helps. Let us know how you get along.
Julie

 

[Racman5487]

Hi Guys,
Thanks for your advice, I do undeerstand haow the CPM works but just didn't
know if there was some strange happenings within the programme or it was my
mistake. I have put the same info into a new project and now have a critical
path, I have obviously made an error with the last one and would love to know
where as it will bug me and also I could learn from it if I could find what
the cause was. I appreciate that it is difficult without seeing the actual
project.

Thanks Again.

 

[JulieS]

Hi Caroline,

You are welcome. If you would like you can zip and email me the file and
I'll take a look and see if I can discover what happened.

If you click on my name in the postings you'll be able to discern my email
address.

Julie

 

[Racman5487]

Hi Julie,
I would love to send the file to you but have tried and just get your
passport no. which the mail system doesn't recognise it as an Email address.

Caroline

 

[JulieS]

Hi Caroline you need to leave out the spaces in the address and convert the
"at" to @ and "dots" to .
If you "dare" post your email address here, I'll send an email to you and
you can just reply. I would post mine but I prefer not to be spammed
unmercifully.