Time Managment 6.4 Estimate Activity Durations:

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Time Managment 6.1 define activities

Time Management 6.2 sequence activities

Time Managment 6.3 Estimate Activity Resources

Time Management 6.4 Estimate Activity Durations:

Time Management 6.5 Develop Schedule:

Time Management 6.6 Control Schedule:

Duration estimating takes information about project scope and resources and develops durations so that a schedule can be developed. Duration estimating has been defined as assessing the number of work periods needed to complete an activity. Estimates should be:

·         Produced by the people most familiar with the work (or at least approved by them). This observation refers to the importance of expert judgment,

·         Progressively elaborated, in other words, estimates will usually become more accurate as the quality of the input data improves

·         Adjusted for the effects of “elapsed time”, (whether or not weekends are treated as work periods). Note: Project management Software makes it much easier to assess the effect of these elapsed times on a project schedule.

Duration estimating should also consider the difference between effort and duration. lf four people work 10 hours each on a task, the total effort that must be paid for is 40 person-hours. lf those four people are working simultaneously, i.e., in parallel, the duration to complete the work will be 10 hours. ln summary, durations are used for scheduling and effort is used to estimate costs, 

Estimate Activity Durations
Inputs	Tools	Outputs
1.       Activity list 2.       Activity attributes 3.       Activity resource requirements 4.       Resource calendars 5.       Project scope statement 6.       Enterprise environmental factors 7.       Organizational Process assets	1.       Expert judgment 2.       Analogous estimating 3.       Parametric estimating 4.       Three-Point estimates 5.       Reserve analysis	1.       Activity duration estimates 2.       Project document updates

 

Seven Key inputs for Estimate Activity Durations:

1.       Activity List: Described in Section 6.l.3.l, durations must be estimated for each activity.

2.       Activity attributes: Described in Section 6.1.3.2.

3.       Activity Resource Requirements: Duration estimates are affected by how many resources are assigned to a task (two people can usually complete a task faster than one person). ln turn, actual availability of those resources is also a major factor. lf resources prove to be unavailable, some form of outsourcing may be required. As mentioned earlier, the relative experience level of the resources may also be a determinant of the planned duration for a schedule activity.

4.       Resource calendars: An output of resource estimating, the calendar would include the availability and capability of all required resources (people and equipment).

5.       Project scope statement: Any constraints or assumptions or assumptions from the scope statement that may affect activity durations. A constraint could be that a key stakeholder has imposed a strict deadline for completion of initial testing. An assumption might be that hurricane activity will not disrupt product testing in your sea coast facility and therefore, you will meet the planned deadline.

6.       Enterprise Environment Factors: Environmental factors that may affect during estimates include:

·         Duration estimating database

·         Productivity metrics

·         Published commercial information

7.       Organizational process assets: Organizational process assets that may affect duration estimates include:

·         Historical information on likely durations

·         Project calendars

·         Schedule methodology

·         Lessons learned

Five key tools for estimate activity duration:

1.       Expert judgment: PMI recommends the use of expert judgment guided by historical information whenever the combination is possible. Expert judgment is crucial because of the potential that can affect durations.

2.       Analogous estimating: A form of top-down estimating, this approach uses the actual durations of previous, similar activities to estimate the duration of future activities. These estimates are usually adjustment by experts for differences in complexity, size and risk. Key points:

·         The technique is usually applied in the early stages of a project when detailed information is limited and is, therefore, considered a ballpark guesstimate (WAG).

·         Developing such an estimate is not costly, but the accuracy is limited.

·         The technique is most reliable when

o   The previous activities are similar in fact and not just in appearance and

o   The individuals making the estimates have the needed expertise (for example, expert judgment was the first tool).

3.       Parametric Estimating: For some tasks, duration estimates can be derived from the quantity needed multiplied by the appropriate productivity rate. For example, if a drawing tasks approximately 10 hours and you need 50 drawings, the estimated during of creating the drawings would be 500 hours.

4.       Three-point estimating: Such estimates can improve accuracy by considering risk. This technique calculates an expected average duration from the following three estimates.

·        Optimistic: The best case scenario as seen by someone familiar with the work.

·        Pessimistic: The worst case scenario as seen by someone familiar with the work.

·        Most likely: The most likely scenario as seen by someone familiar with the work.

·        In similar fashion, a well-known technique for doing the same thing is PERT (Program evaluation and review technique). The differences among PERT, three-point estimate and CPM (Critical path method) will be discussed in the next process on schedule development.

5.       Reserve analysis: Contingency reserves (sometimes referred to as time reserve or buffers) are sometimes added to duration estimates to account for risk or uncertainty. Contingency may be a percentage of the overall schedule or a fixed number of time periods. If used, reserve time should be documented along with assumption and other data.

 

Two key outputs for estimate activity durations:

1.       Activity duration estimate: Quantities assessments of the number of work periods (hours, days and so on) needed to complete an activity (and by extension, to complete the entire project). PMI recommends that these estimates should also include a range of possible results. Note: Duration estimates for different activities are assumed to be statistically independent (the estimate of one task does not determine or Influence the duration estimate of a different task.

2.       Project document updates: Documents that may be updated include:

·        Activity attributes

·        Assumption in the duration estimates.