6th Edition PMBOK® Guide–Process 6.4 Estimate Activity Durations: Inputs

Once we have put all of the activities to be done on a project in a sequence, we need to find out an estimate of their durations to come up with the all-important question, “how long will this project take to complete?”   There are a lot of inputs to this process.   The inputs to the processes of schedule management are like a snowball going downhill:   the outputs of one process become the inputs to the next process and additional inputs from other knowledge areas are also added along the way.

Let’s review all of the inputs to this process 6.4 Estimate Activity Durations.

6.4.1  Estimate Activity Durations:  Inputs  Project Management Plan

The components of the project management plan that are inputs to this process include the schedule management plan, the scope baseline, and several of the project documents.

Let’s discuss the first two of these in the paragraphs below–the project documents are in the next section after this one (see below)

  • Schedule management plan–remember, this is the plan that is an output of process 6.1 Plan Schedule Management that gives guidelines on how to do all of the other processes of schedule management, including this process.   In particular, the guidelines that help with estimating activity durations are:
    • Level of accuracy–the acceptance range used in determining realistic activity duration estimates (is it done in terms of a range of values, in terms of a probability of achieving a certain deadline?)
    • Units of measure–the units of measurement for measuring time (staff hours, or some other unit)
  • Scope baseline–remember this is three documents in one, which includes the project scope statement, the WBS, and the WBS dictionary.   In this process, the activity durations are added to the activities list for each work package in the WBS, and the WBS dictionary may give information on any constraints or available resources which might affect these duration estimates.  Project Doocuyuuments

  • Activity List–contains all schedule activities required on the project which are to be estimated in this process.   This is an output of 6.2 Define Activities.
  • Activity attributes–contains information on each of the activities in the activity list, usually added as updates after the process 6.3 Sequence Activities.   Such updates include the following:
    • Defined predecessor or successor relationships between activities
    • Defined logical relationships between the activities (do they have a Finish-to-Start or series relationship, or a parallel relationship as in Start-to-Start or Finish-to-Finish)
    • Defined lead and lags between activities
    • Other constraints that can influence duration estimates
  • Assumption log–assumptions may contain information on project risks that may impact the project schedule.  The assumption log is an output of the 4.1 Create Project Charter process, but can be updated after the process 6.3 Sequence Activities, and so is an output of that process as well.
  • Resources breakdown structure–shows the resources potentially available for the project broken down by resource category and type.   This is an output of process 9.2 Estimate Activity Resources.
  • Resource calendars–the resource breakdown structure shows the resources potentially available, but their actual availability may vary during the project because they may also be used on other projects or operational work.   The resource calendar identifies when and for how long identified project resources will be available for use on this particular project.   This is another output of process 9.2 Estimate Activity Resources.
  • Resource requirements–how do the potentially available resources meet the requirements of the activities?   If someone with a higher level of skill that is normally required is not available, someone with a lower level of skill to do that same activity may require additional time, or additional resources may need to be assigned to an activity to do it in the same amount of time as it would take if the more skilled resource were doing the activity.   This is yet another output of process 9.2 Estimate Activity Resources.
  • Risk register–along with the assumption log, this contains information on risks which may impact resource selection and availability.   For example, if you are assigning a key person to do an activity, one of the risks to consider is if they have scheduled a vacation or are going to be on a business trip when their work on the project is needed.   The risk register is an output of the risk management process 11.2 Identify Risks.  Enterprise Environmental Factors

  • Published commercial information on duration estimates for standard work done in the industry.
  • Reference databases containing duration estimates for activities done on the project.
  • Productivity metrics  Organizational Process Assets

  • Duration estimates and project calendars from other similar projects (historical information)
  • Lessons learned repository from other similar projects relating to how duration estimates were calculated
  • Policies for creating duration estimates (usually included in the Scope Management Plan)
  • Scheduling methodology (also usually included in the Scope Management Plan)

With all of those inputs, let us now turn to the process itself in the next post on tools and techniques of 6.4 Estimate Activity Durations.


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