Critical Path Analysis

[lk50]

Hi there,

What is the best practice in using critical path analysis and how i
this done in Ms Project?

My understanding is that:

You determine what the end date of the schedule you want it to be b
adding a must finish on contstraint on the final date.

In the total slack column any task that is 0 or below is then on th
critical path.

Is that all there is to it or am I missing something??

Many thank

 

[Rob Schneider]

You have it backwards. Model the project execution from the start with
a series of "as soon as possible" tasks. Project will compute the
completion date.

If that date is not the date you want it to be, then change the plan.
Conceive of a different project plan, strategy, or scope that gives you
the date you want. Or change the date you want.

It's good practice to set a final task milestone (duration=0) to mark
the completion of the project. Set the field called "deadline" for that
milestone task to be your "wanted" date. Project will warn you via the
field "indicator" if your computed end date is "too late".

Probably best to crack open one of the many books available on Project.

--rms

www.rmschneider.com

 

[lk50]

Thanks for your reply Rob.

I understand what you saying - however what I meant was once you hav
the project plan fully sheduled and then you are playing around wit
the end dates whats the best way to find the critical path for example:

the current end date of the schedule is 20/12/09

The Project manager asks what is the critical path to achieve tha
date?

Or

he asks you what would be the critical path if the project had to b
finished on 10/11/09

So what's would be the method to analyse the critical path?

Many thanks

 

[Mike Glen]

Hi lk50,

Welcome to this Microsoft Project newsgroup

I wrote an Introduction to Network Analysis when I started my beginners
series. You might like to see it in the TechTrax ezine, particularly #1, at
this site: http://tinyurl.com/2xbhc or this:
http://pubs.logicalexpressions.com/Pub0009/LPMFrame.asp?CMD=ArticleSearch&AUTH=23
(Perhaps you'd care to rate the article before leaving the site,
Thanks.)

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
MS Project MVP

 

[Rob Schneider]

Humm. Well, for a plan with completion date, say 20/12/09, the critical
path is the critical path. The last task is completion on 20/12/09 You
can show the critical path on the Gantt Chart using the Gantt Chart
wizard. Have you discovered that yet?

Are you clear on what the critical path is? It's the string of
activities that can start/finish without making the project duration
longer. (there are more elegant definitions out there!! this off the
top of my head).

When the PM asks what the critical path is to achieve that date, then
you show him/her the plan with the critical path displayed and ending on
20/12/09.

If then the PM says that the new deadline is 10/11/09, and wants to know
the critical path ... you need to then ask him/her what changes should
be made to the plan. I'm assuming it's the PM's role to decide how the
project is executed. You and the PM should then work together to change
the plan so that the end date ends up on the new desired date of
10/11/09. That will probably mean, since it's earlier, you have to
reduce durations, shed scope, get more people, assume longer work hours
per day ... whatever. Then when you are done, display the critical path.



--rms

www.rmschneider.com

 

[Jack Dahlgren]

The critical path for the project will remain the same no matter when you
want the project to complete. It is calculated by summing the task durations
along all the chains of dependencies. Forcing a different date for the finish
may cause the total slack along that chain to become negative (meaning you
are behind before you have even started) but that chain of tasks has not
gotten any shorter.

As you might expect, doing this requires that the tasks in your project are
connected by appropriate dependencies. With no dependencies, there is no
critical path as each task is independent.

The most useful thing you can do to help analyze the critical path is to
insert the "Total Slack" column. Then try sorting by Total slack and Start.
If you want to shorten the duration of your project, you will have to work on
tasks which have the minimum amount of slack. For an unconstrained schedule
this will be 0. However, if you put a constraint on then it may be less than
0. Work on those first. At a certain point you may find that you have reduced
activity durations on the critical path to a point where another path is
critical. You will then need to work both of those to bring the schedule in.

-Jack Dahlgren