Page 57 - The Six Sigma Project Planner

Estimating Activity Duration
In addition to knowing the dependencies, to schedule the project you also need
estimates of how long each activity might take. This information will be used by senior
management to schedule projects for the enterprise and by the project manager to
assign resources, to determine when intervention is required, and for various other
purposes.

Duration Estimation Guidelines
It is seldom possible to know the activity duration exactly. A given activity duration
estimate can be considered to be associated with a statistical probability of actually
achieving it. In most traditional projects, the activity duration is provided by the person
to whom the activity is assigned; this person usually includes a buffer that can be used
if there are unforeseen, but probable problems. In scheduling and managing projects, it
is helpful to know the magnitude of this buffer. Thus, in estimating the duration of
activities for Six Sigma projects, we ask for not one but three estimates: optimistic, most
likely, and pessimistic. These estimates are defined as follows:
Optimistic duration: the activity duration if the work proceeded exactly according to
plan, with no delays or interruptions.
Most likely duration: the activity duration if we assume a typical pattern of delays and
interruptions.
Pessimistic duration: the activity duration if we assume an unusually large number of
delays and interruptions.
In general, duration estimates should be obtained from the person assigned
responsibility for the activity. However, if this person is not on the project team, he or
she should be made aware of the findings from the research conducted by the team.
This would include research into the duration of similar activities on similar projects.

Note: In traditional project management, people are asked for deadlines or due dates
for their tasks. They are then held accountable for meeting these due dates and
punished if they fail to meet them. Under these circumstances, people will always
provide pessimistic duration estimates. (Wouldn’t you?) In Six Sigma environments, we
develop and manage project schedules based on most-likely estimates or weighted
average estimates (explained below). This means that there’s a good chance of not
meeting the projected task duration. Thus, although the project schedule must be
managed, failure to meet a task duration target must be tolerated. Statistically, the
project due date will be met if the average task duration is relatively close to that
predicted.

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