Numerous projects was unsuccessful
to meet schedule prediction
because of lack of schedule development to overcome
this. There are methods which are used for project schedule. Such as critical path method and PERT method
1. Critical path method (CPM)
Critical path method or critical path analysis
method. It is a network connection diagram approach
used to approximate total project
time duration. The network diagram chart will have the nodes which having connection
.used forward pass and backward pass approach to find the rout .This tool will
help you reduce project schedule
overruns. A critical path for a project is the series of activities that
determine the earliest time by which the project can be finish. There are many tasks done in equivalent on projects, and most of projects have several paths through a network diagram chart.
The longest path is nothing but critical tasks is what is driving the
completion date for the project. You are not finished with the project until
you have finished all the tasks.
For calculating the Critical Path for a
project, we must
Create a network diagram which requires a
activity list which is project based .After creating a network diagram chart,
we must also approximate the duration of each activity to determine the
critical path. Calculation of critical path involves adding the time durations
taken by all activities on each path through the network diagram. The longest
path is the critical path.
The critical path is the chain of activities with
the longest time taken duration. A slow up in
any of these activities will result in a delay for the whole project. this critical path example help us
to understand the how this method work.
Using the Critical Path Method (CPM)
duration of each activity is listed above each node in the diagram. For each
path, add the duration of each node to determine it’s total duration. The
critical path is the one with the longest duration.
are three paths through this project.
-> Activity1->Activity3->Activity4->finish 3+7+2=12
-> Activity2->Activity3->Activity4->finish 5+7+2=14 (Critical Path)
-> Activity2->Activity5-> finish 5+4=9
Advantages of CPM
Makes dependencies visible between the project
Increases visibility of impact of schedule revisions
Enables the Project Manager to optimize efficiency
Disadvantages of CPM
For large and complex projects, there’ll be thousands of
activities and dependency relationship
The Critical Path Method does not account
for resource and resource allocation
2. Program Evaluation and Review Technique (PERT)
PERT was initially used by defiance in their Polaris
project .In this method, the activities time duration is found using these following
Standard Devation =
A network analysis method is used to approximate
project time duration when there is a unpredictability
about the individual activity time duration approximates. PERT applies the
critical path method (CPM) to a weighted average time duration approximate.
This approach was developed about the same time as CPM, in the late 1950s, and
also uses network diagrams concept, which are still sometimes referred to as
PERT charts. PERT uses probabilistic time approximates duration. Approximation
based on using optimistic time, most likely time , and pessimistic time approximates of activity durations instead of
one specific or discrete duration approximate, as CPM does .By using the PERT
weighted average for each activity duration approximate, the total project
duration approximate takes into account the risk or uncertainty in the
individual activity estimate.
Suppose A project team in the project case
used PERT to determine the schedule for the online application registration
system project. They would have to collect data for the optimistic, most
likely, and pessimistic duration approximates for each project activity. Suppose
one of the activities was to design an input screen for the system. Someone
might approximate that it would take about two weeks or 10 workdays to do this
activity. Without using PERT, the duration approximate for that activity would
be 10 workdays. Using PERT, the project team would also need to approximate the
pessimistic and optimistic times for completing this activity. Suppose an
optimistic approximate is that the input screen can be designed in eight workdays,
and a pessimistic time approximate is 24 workdays.
Applying the PERT formula:
PERT weighted average =
Instead of using the most likely duration approximate
of 10 workdays, the project team would use 12 workdays .These additional two
days could really help the project team in getting the work completed on time.
Advantage of PERT
A PERT chart makes planning
large projects easier
PERT is a way of making
relationships visible in a diagram
PERT makes the critical path
Disadvantage of PERT
PERT charts can be
complicated and confusing, with hundreds or even thousands of tasks and
PERT diagrams can be expensive
to develop, update and maintain.
PERT charts depend on the
ability to predict precise time frames for multitudes of tasks