Scheduling is a distinctly separate activity from
estimating even though it depends upon accurate estimates. It
is the process of converting direct hour estimates into date
schedules. Scheduling includes the assignment of resources to
tasks in the correct sequence to meet the objectives of the
project. This is a complex process and one that is almost
impossible without automation. In most organizations, there are
many projects, resources and environmental conditions that can
influence projects and cause the need for changes in schedules.
Scheduling is an iterative process of balancing the
resources available against the time requirements established
for the project. There are several variables involved:
- The direct hour estimate, either O-O-M or detail.
- The methodology for the project, as defined by the key events
of the project.
- The human resources to be used on the project, with their
effectiveness rate, current schedule, and skills and proficiencies.
- Project priorities as established by executive management.
- A corporate calendar which notes weekends, holidays, shutdowns, etc.
As an example of how a schedule is calculated, assume that
there is a professional working on an assignment with an
estimate of 100 direct hours. If the individual's planned
effectiveness rate is 70%, then the 100 hour estimate converts
to a projected 142.85 elapsed hours required to complete the
assignment. The elapsed hours in the normal business day is
divided into the 142.85 and (using 8 hour work days) results in
17.85 business days required to complete the assignment. These
17.85 business days are applied to the corporate calendar which
expresses weekends and holidays, also other commitments for the
professional, such as vacations and other work assignments.
Taking these into account, start and end dates are then determined.
If the end date is unsatisfactory to the manager, there are
several possible alternatives which can be used to improve the
schedule:
- Reduce the employee's indirect activities and increase their
effectiveness rate.
- Schedule work on weekends and/or holidays.
- Add additional personnel or use alternative personnel.
- Increase the number of available hours in the business day
(within reason of course).
- Or combinations of the above.
By understanding and adjusting the variables associated
with a project, a project manager has the ability to play "what
if" with a high degree of certainty.
Scheduling is an activity that is greatly influenced by the
concept of effectiveness rate. By examining the use of time,
both direct and indirect, realistic schedules can be prepared.
The "man hour" approach mentioned earlier does not take the
environmental influences into consideration and assumes an
effectiveness rate of 100%. Under this approach, the sample
schedule would be completed in 12.5 business days as opposed to
the 17.85 days mentioned. The difference is that effectiveness
rate builds reality into the schedule. It does not make use of
some esoteric "fudge factor" as typically used in relation to "man hours."
