34

Project Management

Planning the Time Dimension

When planning the time dimension, the objective is to

determine the shortest time necessary to complete the

project. Begin with the WBS and determine the time

necessary to complete each step or subunit. Next, determine

the sequence in which steps must be completed, and which

steps can be underway simultaneously. From this analysis,

you’ll determine the three most significant time elements:

X The duration of each step

X The earliest time at which a step may be started

X The latest time by which a step must be started

Planning the time dimension can be done only by people who have experience with

the activities designated for each step. If you personally don’t know how long it

takes to do something, you need to rely on someone who does have the requisite

experience.

Many project managers find it realistic to estimate time intervals as a range rather

than as a precise amount. Another way to deal with the lack of precision in

estimating time is to use a commonly accepted formula for a task. If you’re working

with a mathematical model, you can determine the probability of the work being

completed within the estimated time by calculating a standard deviation of the time

estimate.

DO NOT ALTER OR DELETE THIS LINE – It is here for spacing purposes.

DO NOT ALTER OR DELETE THIS LINE – It is here for spacing purposes.

PLANNING THE TIME REQUIRED

When you’re involved with a project, how do you estimate the time required for

its completion?

________________________________________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________

DO NOT ALTER OR DELETE THIS LINE – It is here for spacing purposes.

DO NOT ALTER OR DELETE THIS LINE – It is here for spacing purposes.

35

3: Planning the Project

Using a Mathematical Model to Estimate Time

T

m

—The most probable amount of time necessary to complete the project.

T

o

—The optimistic (shortest) time, within which only 1% of similar projects are

completed.

T

p

—The pessimistic (longest) time, within which 99% of similar projects are

completed.

T

e

—The calculated time estimate.

T

o

+ 4T

m

+ T

p

T

e

=

6

ı = Standard deviation

T

p

- T

o

ı =

6

The work will be completed within the range of T

e

± 1 standard deviation or 68.26%

of the time.

The work will be completed within the range of T

e

± 2 standard deviations or

95.44% of the time.

The work will be completed within the range of T

e

± 3 standard deviations or

99.73% of the time.

With a duration set for each subunit, the next step is to determine the earliest and

latest times for starting each one. Gantt charts and PERT diagrams are two methods

commonly used to chart a project. Both are discussed in the pages that follow.

36

Project Management

DO NOT ALTER OR DELETE THIS LINE – It is here for spacing purposes.

DO NOT ALTER OR DELETE THIS LINE – It is here for spacing purposes.

PRACTICE ESTIMATING TIME

For the same project that you’ve been using, determine a time estimate for each

of the project’s subunits or steps.

Subunit or Step T

o

T

p

T

m

T

e

DO NOT ALTER OR DELETE THIS LINE – It is here for spacing purposes.

DO NOT ALTER OR DELETE THIS LINE – It is here for spacing purposes.

Start Free Trial

No credit card required