Float On: Free Float, Total Float, & Slack

Please pardon the interruption, folks. My paying job has had me hopping with deliverables, and I wasn't able to whip out a high-quality post in time for publication last week. I'm sure you missed me.

But having missed a week posting being a big fat slacker offers the perfect opportunity to segue into my next topic, which is "slack," AKA "float" in tasks for a given project. I referenced it in my last entry as "total float." (Which, incidentally, sounds really relaxing... something I'd like to be doing, in a pool, perhaps with an umbrella drink in hand.)

"Float" is a pretty important concept in Critical Path Management. It's basically the amount of time you can let a project task slip before it adversely affects other tasks or your whole project. If you can, imagine your project tasks, linked by dependencies, as pieces of rope all tied together (a Gantt chart gives you a pretty good visual here). When you have slack in your rope, you have some leeway, and so it is with project management. With slack, your project isn't necessarily stretched to its utmost limit.

You have a couple of different kinds of slack, or float (the two can be used interchangeably, apparently, though I'm not sure if one or the other is more fashionable among genuine PMs). First, there's "free float" (which also sounds pleasant). This refers to a permissible delay that will not adversely affect subsequent tasks in a project.

Then there's the aforementioned "total float," which is associated with the path as a whole and is the sum of the total free float values in a given path.

Clear as mud? Well, have a look at the diagram and brief example on this Wikipedia page. Yes, yes, we all know that Wikipedia is a suspect source, but when I was discussing this week's topic with Mike Taylor, CEO of Innovative-e, he emailed that very link to me. And he's a bona fide Project Management Professional.

But if you don't trust Wikipedia as a source, check out this article on Microsoft's Office site.

Because this is such a key concept for Critical Path Management, you'll want to read and re-read (and then read some more) so you really internalize the idea and come to understand how float can change the landscape of your entire project.

Posted Aug 21 2012, 10:00 AM by Pamela Flora | Edit this post

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About Pamela Flora

Pamela Flora is currently the Marketing and Administrative Coordinator for the D.C.-area office of Innovative-e, Inc., where she has worked since March 2011. She has previously enjoyed work in both the public and private sectors as a technical writer, as well as taking the occasional freelance gig. While her current duties encompass a plethora of tasks both mundane and complex, they did not include project management until recently, when she was given the opportunity to explore project management from an in-the-trenches POV and document the experience in this blog. In her spare time, Pamela likes to hang out with her five kids, paint, write, spend quality time with her DSLR, and, now, read project management books. Though she is only infrequently on Twitter, you may follow her there just in case she feels compelled to tell you what she had for breakfast and you feel the strong desire to know: @puckish222.

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