Manually determining the critical path

[Ginger]

Hi All,

I know that Microsoft creates the critical path based on start and finish
dates, dependencies and 0 slack. When I select the view for Critical path it
is not exactly what I know to be the critical path. Can someone coach and
guide me how I can traverse through my 4000 line plan to manually determine
how microsoft calculated the critical path. Do I start at the bottom of the
plan or at the beginning and what am I looking for?? I know that MSP is
looking at the zero slack but I am also not sure how microsoft project
determines that something has a zero slack.

Thanks, Ginger
P.S. I think this is a really great board for answers.

Thanks, Ginger

 

[DavidC]

Hi Ginger,

My first step would be to make sure that all activities have both a
predecessor and a successor. If one of the tasks in the stream of activities
you consider should be on the ctirical path does not have a successor then it
will calculate it's slack to the end of th project as stated under Project,
Project Information. Also make sure that the end date for the project uner
the project information is in fact the end date shown by the very last task.
To that end I always have an activity called Proejct end and then every end
task is linked into that to make sure that there is only one end date to the
project.

Next I would change the number of days slack which Project considers to be
critical. Go to Tools, Options, Calculation and change the number of days
considerd to be critical from 0 to say 2 and then see what the critical path
is. It is conceivable that your project critical path is eactly as you
expect it just might have some slack in it because of the interrelationship
between tasks and parallel activities. In a 4000 task programme that is ver
likely.

Hi All,

I know that Microsoft creates the critical path based on start and finish
dates, dependencies and 0 slack. When I select the view for Critical path it
is not exactly what I know to be the critical path. Can someone coach and
guide me how I can traverse through my 4000 line plan to manually determine
how microsoft calculated the critical path. Do I start at the bottom of the
plan or at the beginning and what am I looking for?? I know that MSP is
looking at the zero slack but I am also not sure how microsoft project
determines that something has a zero slack.

Hope this helps

Regards

DavidC

 

[Rod Gill]

If any task has a large amount of total slack, then you may have a missing
link. make sure that only Tasks that are inputs to the schedule have any
constraints. Constraints change the critical path. For example if there is a
management meeting that will provide permission to proceed, I would have a
summary task at the top of the schedule where all input events with dates
reside. No tasks under that should have a constraint other than as soon as
possible.

 

[Steve House [Project MVP]]

I'm curious - you say Project does not agree with "what you know to be the
critical path." But how do you know that what you think is the critical
path really is it? What criteria have you used to determine what tasks are
critical and what tasks aren't? Remember, the critical path is essentially
the longest sequence of tasks, the longest chain of events through the
project. The total duration of the critical path is the duration of the
project itself. It doesn't have anything to do with importance or
milestones or anything else - its simply the sequence of events that
determines the project's total length.

 

[Rick Williams]

When trying to determine what your critical path is - the suggestions here
are good ones, particularly making sure there are no missing links and that
your project has only one end task. Also make sure that there are no "Must
Start On", "Must Finish On", or any other type of constraint dates.

One other very important point - how often is the project updated? If it is
updated weekly, then any task with less than one week total slack could be
"critical" next week. If your reporting period is one month (too long!),
then any task with less than a month's worth of slack could be critical
after the next update.

Regards,
Rick Williams

 

[Mike Glen]

Hi Ginger,

If you want to get back to basics with your undestanding of Critical Path,
you might like to see FAQ Item: 42 on Network Analysis.

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
Project MVP

 

[davegb]

If any task has a large amount of total slack, then you may have a missing
link. make sure that only Tasks that are inputs to the schedule have any
constraints. Constraints change the critical path. For example if there is a
management meeting that will provide permission to proceed, I would have a
summary task at the top of the schedule where all input events with dates
reside. No tasks under that should have a constraint other than as soon as
possible.

--

Rod Gill
Project MVP
Visit www.msproject-systems.com for Project Companion Tools and more

Interesting idea, Rod. Never thought about putting all constrained
tasks under a special Summary line. I usually just filter for them, but
your method would allow me to see the and the tasks they're linked to.
I guess another advantage would be that they're all in once place and
anyone looking at the Gantt would pretty much have to be aware of them.
Any other advantages?