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MSP 2013

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    Siddharth
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    What is the difference between critical path and critical chain? Can we get critical chain from MSP 2013?

    #414326 Reply

    Critical Path Method
    o Phases complete sequentially, e.g. documents produced before build and test
    – E.g. construction drawings approved before site is cleared
    o Unlimited resources, e.g. contracted workers
    o Appropriate for projects that have to complete full scope and be completed by a fixed product delivery date, allowing for agreed to risks
    o Typically estimated with conservative durations that may allow for delays from issues and risks that actually occur
    – Workload not leveled. Workload not aggregated across the organization’s project portfolio; so, approval of projects in excess of resource capacity causes all projects to slow down, as occurs in rush hour traffic.
    – Human nature: try to finish on time, delay actual start until remaining time is minimal, so surprises delay task finish, on-time delivery usually involves late delivery or heroic efforts toward the end of development and test

    Critical Chain Method
    o Phases complete sequentially, e.g. documents produced before build and test
    o Limited resources, e.g. employees
    o Appropriate for projects that have to complete full scope in the minimum time
    o Typically estimated with ranges of workhours and resource assignment units so MS-P calculates the durations
    – Part of the difference between delivery date using conservative estimates and using median estimates is entered as an uncertainty buffer using a “Start No Earlier Than constraint” on the product delivery task. The buffer covers the chance that more than half the tasks exceed their median estimates. Issues and risks are not covered in the workhour estimates.
    – Project is scheduled using median (not conservative) estimates and an uncertainty buffer is applied just ahead of the product delivery task (and after a lag as an Aggregate Risk Contingency to absorb delays from any risks that actually occur)
    – Issues covered by Change Management. Risks covered by an Aggregate Risk Contingency or by Monte Carlo simulation.
    o Workload is leveled before execution and after each updating
    o Project is managed by uncertainty buffer penetration: if penetration exceeds 1/3 a recovery plan is developed, if penetration exceeds 2/3, recovery is implemented to restore the buffer as then needed.
    – Buffer management causes uniform workload through out the project, avoiding heroic burn-out
    o Because the project is executed using median estimates and the uncertainty buffer is less than the sum of buffers within each task, the schedule is shorter than a Critical Path schedule with limited resources that is estimated with workhours and assignment units so it can be leveled.
    o Because the project is managed by uncertainty buffer penetration, the delivery date is sooner and more reliable than from a Critical Path schedule that is leveled

    Agile Method (a form of the Rolling Wave method that uses different vocabulary)
    o Appropriate for projects that need to produce as much functionality as possible with limited resources and fixed finish date
    – Incremental approach allows for evolving scope as customer needs evolve and technology reveals itself
    – Deferred functionality may be pushed to an enhancement project
    o Documentation is supposed to be gathered as functionality accumulates
    o Segmenting build and test into fixed duration “sprints” provides uniform workload through out the project, avoiding heroic burn-out

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