Critical Path not showing as expected

[Helen]

Hi,
I'm using Project 2002.

I've got a series of tasks, with a lot of dependancies, and a resources of 2
man days performing the tasks. I have leveled the tasks so that the resources
are not overallocated and have then asked Project to show me the critical
path, expecting the series of red (instead of blue) bars to always finish and
start as the pervious tasks finished and started. Instead, alot of my
dependancy arrows ahve turned red, but only 3 of my 22 bars have turned red.
There appears to be a lot of time between these tasks which has not been
considered to be on the critical path. I'm quite confused as to what is
wrong. I even started again incase I'd put a strange dependacy in which would
cause this, but can see nothing. Any thoughts?

Thanks
Helen

 

[Steve House]

Do you have actual work entered into the plan? Do you have constraints on
the tasks, perhaps created by entering task start and/or end dates instead
of letting Project freely calculate them for you?

 

[Helen]

Steve,

I do have work entered into the plan. Each task has only a time, none of
them have specific start or finish dates. I have leveled the project so that
the tasks are freely moved by MS Project to create the best possible project
plan. And I can sit here and look at the plan and point out the critical
path, yet when I try and get the program to calculate it, it will only show
some of the path as being critical.

Helen

 

[Steve House]

If you have actual work entered so some tasks are shown as in progress or
complete, that can effect the critical path. Also manually entering
ANYTHING in the Start or Finish columns, be it dates, times, or both will
set Start No Earlier Than constraints on the tasks which will also impact
the calculation of the critical path. The simplest plain language
definition of a critical task is one that if it were delayed, it would delay
the project completion (there's more to it but that's the basic definition).
If it could be delayed by even one minute before effecting the project
completion, it's not critical. So imagine a simple project with three,
1-day duration tasks that starts on Monday. They're linked in succession
A->B->C. Put a Start No Earlier Constraint of Wednesday on Task B . A
starts and ends on Monday. B on Wedsday, and C on Thursday and the project
ends at the end of the day Thursday. Nothing is happening on Tuesday. You
could also start it Monday at 1pm or you could start it Tuesday at 8 and the
project finish will still remain at the end of the day Thursday. Task A is
not critical and does not lie on the critical path. B and C ARE critical
because any delay at all, to either one of them, will cause the project
completion to be delayed. Because of the constraint on Task B, the critical
path does NOT run all the way from start to finish but instead picks up in
the middle of the project with Task B. Only when you delay A to start past
the start of the day on Tuesday does it become critical with all three tasks
showing on the critical path.

Look again at your start and finish fields. ALL date fields in Project are
date/time fields without exception. In the View tab of the Options menu you
can choose a date format that displays only the date component, only the
times, or both, but both a specific date and specific time are ALWAYS there.

If you have actual work entered into the plan you MUST have dates, even if
they're hidden. Work is a visible physical action and it always happens at
a specific time in history. If you painted a wall, you might have done it
last Tuesday or last Wednesday or between 10am and 2pm on the 18th of June
but whenever you did it, it was an activity that took place between two
exact and knowable points in time.

 

[Mike Glen]

Hi Helen,

Welcome to this Microsoft Project newsgroup

The clue comes in the levelling. When Project levels, it delays a task
until the resources are available. If there is a delay on the task, it
cannot be critical as the delay is, in effect, slack. Only tasks with zero
slack are critical. Try inserting a Column for Total Slack to confirm this.

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

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

Mike Glen
MS Project MVP
See http://tinyurl.com/2xbhc for my free Project Tutorials