- A means to develop a project schedule to show the interrelationship
between and among, milestones, and tasks in an entire project. - An easy to understand road map of the necessary activities and their
necessary start times and completion
NETWORK ANALYSIS
- In 1958, the U.S. Navy’s Special Projects Office, together with aerospace
company Lockheed Missile Systems and consultancy firm Booz Allen &
Hamilton, developed Program Evaluation Review Technique (PERT) for the
Polaris missile program. - It was a tool to ensure the completion of the Polaris program during the Cold
War when the U.S. government was concerned about the Soviet Union’s
growing number of nuclear weapons.
PROJECT EVALUATION AND
REVIEW TECHNIQUE (PERT)
- is a project modeling technique that was
developed in 1956 during the joint venture between the El DuPont
chemical company and computer firm Remington Rand Univac. The
CPM was devised to tackle the interrelationships of separate activities
within a project schedule. - This method was first tested in 1958 on a project to construct a new
chemical plant.
Critical Path Method (CPM)
PERT made use of the recently developed
Critical Path Analysis techniques,
- Powerful tools that help schedule and manage complex projects
- Graphical portrayal of activities and event
- Show dependency relationships between tasks/activities in a
project - Clearly show tasks that must precede (precedence) or follow
(succeeding) other tasks in a logical manner
PERT AND CPM
- a single estimate for activity time used that does not allow for variation in activity times
- Activity times are assumed to be known or predictable
(“deterministic”)
CPM
- multiple time estimates are
used for each activity that
allow variation in activity
times (optimistic time, most
likely time and pessimistic
time). - Activity times are assumed to be random, with assumed
probability distribution
(“probabilistic”)
PERT
Project scheduling by PERT-CPM
consists of three basic phases:
- Planning
- Scheduling
- Control
- breaking down the project into distinct activities;
- determining the time estimates for these activities;
- constructing a network diagram with each box
representing the activity;
PLANNING
- constructing a time chart showing the start and the finish times for
each activity as well as its relationship to other activities in the
project; - pinpointing the critical (in view of time) activities that require
special attention if the project is to be completed on time. - showing the amount of slack (or float) times for the non-critical
activities;
SCHEDULING
- Manage the project using the Critical Path
- “Crash” the critical path to reduce project duration
- Project crashing is a method for shortening the project duration
by reducing the time of one (or more) of the critical project
activities to less than its normal activity time. This reduction in
the normal activity time is referred to as crashing.
CONTROLLING
This reduction in
the normal activity time is referred to as
crashing.
ADVANTAGES OF PERT/CPM
- It compels managers to plan their projects critically and analyze all
factors affecting the progress of the plan - This allows managers to focus process improvements on the tasks
that are most vital to the timely completion of the project - Especially useful when scheduling and controlling large projects
DISADVANTAGES OF PERT/CPM
1.The technique relies on past data and experience to formulate
completion time predictions
2.A weakness of CPM is that it focuses primarily on the time aspect
of activities, neglecting other concerns, such as quality and cost
control.
3.Uncertainty about the estimate of time and resources. These must
be assumed and the results can only be as good as the assumptions
(PERT)
Project Evaluation and
Review Technique
(CPM)
Critical Path Method
breaks down the project
into small set of activities. It represents a closed mechanical system model
which assure that the short-term future is fixed and predictable. However, in reality, good project
management regularly adjusts to contingencies
PERT/CPM
presents a graphic illustration of a project as a network diagram consisting of numbered nodes
(either circles or rectangles) representing events, or
milestones in the project linked by labelled vectors
(directional lines) representing tasks in the project.
PERT chart
represented by
arrowed lines between
the nodes or circles
Activities
- a deterministic method that uses a fixed time
estimate for each activity. - tool to analyze project and determine
duration, based on identification of “critical
path” through an activity network. - knowledge of the critical path can permit management of the project to change duration.
CRITICAL PATH METHOD (CPM)
enables optimal management
of resources like
reassigning to
responsible persons.
CRITICAL
ACTIVITIES
Can be replanned,
rescheduled, and
resources can be
reallocated flexibly
without affecting the
whole project
NON-CRITICAL
ACTIVITIES
-Graphical portrayal of activities and event
- Shows dependency relationships between
tasks/activities in a project
- Clearly shows tasks that must precede
(precedence) or follow (succeeding) other
tasks in a logical manner
Network
any portions of project (tasks) which required by
project, uses up resource and consumes time –
may involve labor, paper work, contractual
negotiations, etc.
Activity: represented as nodes
