TIM: question on free slack

Discussion in 'PMP' started by _19325, Feb 26, 2018.

  1. _19325

    _19325 Well-Known Member

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    Hi Tim. I just want to verify something that I read on a project management book regarding free slack. The book specifies that free slack can only happen on the last activity of a chain that feeds into the critical path. Is this true? The PMBOK (5th edition) says that free slack is "the amount of time that a schedule activity can be delayed without delaying the early start date of any successor or violating a schedule constraint", but it doesn't specify that it can only happen on the last activity on a chain that feeds into the critical path. That other project management book that I read is based on the 6th edition.
     
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  2. tim jerome

    tim jerome Well-Known Member
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    The definition of free float (please forgive me, I call it float instead of slack) is the allowable slippage before this activity impacts its successor. If you have a non-critical successor, its early start will still be impacted. The scheduling practice standard states "... free float indicates how lack of progress impacts immediate successors..."

    Total float is impact to the end of the project. In effect, considering all of this, you can say that free float can occur due to both critical and non-critical successors. If activity A has 1 day of float and activity B has 4, if A slips 2 days, that extra day is carried to B (that's the effect of overstepping your free float) and still not impact the project's end - as long as activity B doesn't slip more than 3 days.

    Understand that I'm describing a fundamental description of the Critical Path Method and float, and other environments may demonstrate different. Under the Critical Path Method, float (including total, free, as well as independent) is an attribute of an activity and its relationship to the activities around it. This is what you'll be tested against.
     
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  3. _19325

    _19325 Well-Known Member

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    Thanks Tim, that clarified it!
     
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    Last edited: Feb 26, 2018

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