Difference between PERT and CPM

Difference between PERT and CPM

1. The two scheduling methods, uses common approach for designing the
network and for ascertaing its critical path. CPM is different from PERT in a way that
the former concentrates on time while the latter stresses on time-cost trade-off. In the
same manner, there are many differences between PERT and CPM, which we are going
to discuss below.
Parameters PERT CPM
Basic Concept A Probabilistic model with
uncertainty in activity duration.
Expected duration is calculated
from to, tm, tp
A deterministic model
with well known activity
duration based upon past
experience
Estimates Three time estimates (optimistic
time, most likely time and
pessimistic time)
Single time estimates
Orientation Network is constructed on the
basis of Events
(Event oriented)
Network is constructed on
the basis of jobs or
Activities
(Activity oriented)
Nature of job Non repetitive nature
Exp: Research and development
project, Defence project
Repetitive nature
Exp: Civil construction,
industrial setting, plant
maintenance, Ship
building
Focuses on Time
(meeting time target or
estimating percent completion is
more important. Resources are
always made available as and
when required)
Time-Cost trade off
(Optimising cost is more
important. there is better
utilisation of resources)
Crashing Not Possible
(as there is no certainty of time
activity duration cannot be
reduced
Possible