What exactly is project or task "slippage"?

[Andy S.]

I'm setting up a project and I think I have slippage that will impact the
critical path. What exactly is the definition of "slippage?" And what did I
do wrong that's causing nothing to show as critical path?

 

[DavidC]

Hi Andy,

Slippage is where a task does not or cannot start on the date scheduled to
start. The slippage can be a problem if the slippage means that the critical
path has emant that the project end date cannot be met. Other situations
might simply mean that there is less float than originally planned. An
example: On a project I am working on we had a pump being manufactured which
had three months of float, the manufacturing slipped by one month and hence
left us with 2 months of float. This posed no problem at all. However I now
have a sequence of tasks where there was 13 days of float, and now remedial
works menas that this work has now slipped and all that float and more will
be used up. Unless some other means of completing the downstream tasks, then
the project end date will not be met.
Now for the critical path. This is the path with the least amount of float
available. If the default setting is not changed then you may not 'see' a
critical path. Two things need to be set:

First format the bars to show a critical task as a colour other than blue.
Simply add another format style, for tasks that are "Normal,Critical", then
set the colour to whatever you desire. Convention often has this as red to
stand out. Now under tools/options/calculation, set the critical path to be
any task with a float of less than say 5 days or whichever you consider is
appropriate for the project. On a short duration project such as maintenance
over two weeks, then anything with less than one day float maight be
considered critical, whilst on a two year project that could be extended out
to say 20days. It is how course or fine you want to identify those tasks
which will impact on the project if they slip by more than their float less
the period set under the options.

Hope this helps.

Regards

DavidC

 

[DavidC]

Andy,

Sorry but one other thing. Does your project have an end date by which it
needs to be completed? If it doesn't then slippage on a task may not alter
the float since the task may simply push the end date out further. I will
often set a deadline to show the end of the project and that will then ensure
that any slippages will reflect in reduced float.

regards

DavidC

 

[davegb]

I'm setting up a project and I think I have slippage that will impact the
critical path.  What exactly is the definition of "slippage?"  And what did I
do wrong that's causing nothing to show as critical path?

Slippage is when a task is no longer starting on it's Early Start
date. ES is calculated by doing the Forward Pass during a Critical
Path Method analysis. ES is the earliest a given task can start given
it's dependencies and their durations. Late Start is the latest date
the task can start and still have the project finish as scheduled. The
difference between the two is Total Slack.
TS = LS - ES
A task with zero TS is Critical, normally. In Project, you can set the
Critical Path Threshold to some number larger than zero, though this
is rarely done.
All these calculations are automatically done by Project every time
the schedule changes (if Calculation is set to automatic, which it
usually should be). All of the numbers it generates are available in
Project if you know how to expose them. This includes ES, Early Finish
(EF), LS, LF, TS and Free Slack (FS) as well as others. Understanding
and using these I call the "unknown" part of Project because 90% of
users have no idea what they are or how to use them. This means that
they're not getting at least 90% of the value of having a schedule.
It's not just a pretty picture to hang on the wall.
If you want to be able to use Project effectively, you need to
understand CPM theory at least some, and what these terms tell you
about your schedule. Spending a couple of hours learning CPM and how
Project applies it will pay off many times over in planning and
managing your projects. I highly recommend it. There's lots online on
this, and several good books. I recommend Lewis' "Project Planning,
Scheduling and Control" as an excellent starting point.
I also recommend, if you can find it, taking a Project class FROM AN
INSTRUCTOR WHO UNDERSTANDS CPM and has actually managed projects.
There are a lot of pushbutton instructors out there teaching this
software without a clue as to how it is used. Find one who understands
it, even it you have to travel to take the course.

Hope this helps in your world.

 

[GuitrDad]

One more place to look...

I have seen inexperienced MS Project users create schedules with all start
and/or finish dates constrained (i.e., "hard-coded"). This does not provide
Project the ability to calculate a critical path. Make sure to use
predecessors/successors in sequencing your work.

Joe

 

[salgud]

One more place to look...

I have seen inexperienced MS Project users create schedules with all start
and/or finish dates constrained (i.e., "hard-coded"). This does not provide
Project the ability to calculate a critical path. Make sure to use
predecessors/successors in sequencing your work.

I have seen EXPERIENCED MS Project users create schedules with all start
and/or finish dates constrained!
As a wise lady told me many years ago, there's a big difference between 20
years experience and one years experience repeated 20 times!