Project - Invalid Critical Path

[Alison]

Hi,

I am working on an assignment and need to display the
critical path of my project. When I format the gantt chart
to display the critical path, only the last 4 tasks are
coloured red. Project does not seem to recognise that
there are other tasks that will also be in the critical
path. I have a couple of tasks that use 'Finish No Earlier
Than' and have heard of problems with this in Project 98.
I am using Project 2002 and have tried changing
the 'Finish No Earlier Than' referenes to other types but
this makes no difference.

Any suggestions???? Please help!

Alison

 

[Rod Gill]

For safety all tasks should have the constraint As Soon As Possible. Date
should only ever be calculated by entering durations and links. You can of
course enter a project start date under Project, Project Properties.

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[Gérard Ducouret]

Hello Alison,

If you set a 'Finish No Earlier Than' constraint on a task on the critical
path, you probably introduced some slack between this task and its
predecessors. The definition of Critical task is "slack = 0", so the
predecessors are no longer on the critical path.

Gérard Ducouret

 

[Steve House]

That's one of the issues around constraints to indicate deadlines, etc, they
can introduce distortions in the critical path. Not that you shouldn't use
constraitns when they accurately model the project of course. It's
completely possible for the critical path to pick up in the middle of the
project. Lets say we have 5 tasks A->B->C->D->E each one week long. A
starts the first of April, B a week later, so somewhere around the 15th of
April we're ready to go on to C. But C must be done at a facility that
isn't available to us until May 1st so C has a "must start no ealier than"
constraint on it. This is a perfecftly valid use of the constraint. Even
though we're READY to go on April 15th, we can't until May 1. So that means
that A or B could be delayed as much as 2 weeks before they start to push
back C. But what's a "critical task?" Simply one whose delay will delay
the project completion. Since A & B can be delayed some period of time
before they affect the tasks C and beyond, they're not critical and the
critical path starts up at C. OTOH, if they get delayed so that they finish
after 01 May, now suddenly they will become critical.

Hope this helps

 

[Alison]

Thanks very much. I think my problem is just that tasks
that form the longest path through the project do have
some slack around them. As such they are not
really 'critical path'.

Thanks again,

Alison