11 PERT, CPM and GANTT
Implementing pert
The first step to scheduling the project is to determine the tasks that the project requires and the order in which they must be completed. The order may be easy to record for some tasks.
Alternative to CPM...
An alternative to CPM is the pert project planning model which allows a range of duration to be specified for each activity.
About the network diagram
- A network diagram can be created by hand or by using diagram software. - There are two types of network diagrams: 1. AOA - Activity on arrow 2. AON - Activity on node
What does the CPM model do?
- CMP models the activities and events of a project as a network. - Activities are shown as nodes on the network. - Events that show the beginning/end of activities are shown as lines.
cons of GANTT chart
- Does not show dependence/interrelationship of one activity to the other. - Critical path not easy to determine. - Hard to show slack time. - Cumulative effect of delays hard to show. - Problem in large project: chart becomes impractical and cumbersome, both in drawing and updating.
GANTT
- Gantt shows the duration of tasks whereas CPM/PERTT shows the sequence and dependencies between tasks. - Gantt shows the time overlap of tasks whereas CPM/Pert does not show which tasks can be done in parallel.
What benefits does it provide?
- Provides a graphical view of the project - Predicts the time required to complete the project - Shows which activities are critical to maintaining the schedule and which are not.
cons of Network analysis
- Timescale is unclear because chart is not drawn to scale. - Chart itself cannot record progress. - Current position is not immediately obvious.
Steps in CPM planning
1. Specify the individual activities 2. Determine the sequence of those activities. 3. Draw network diagram. 4. Estimate completion time for each activity. 5. Identify the critical path. 6. Update CPM diagram as project progresses.
Activity on node
Generally easier to create and interpret.
What does PERT stand for?
P - Program E - Evaluation and R - Review T - Technique
What is PERT?
Pert is a method to analyse the involved tasks in completing a given project, especially the time needed to complete each task, and identifying the minimum time needed to complete the total project.
What is crashing?
Reducing time on activity completion time is known as "crashing", the activity to illustrate this concept is "Activity on node".
CPM vs PERT
CPM was developed for complex but fairly routine projects with minimal uncertainty in the project completion times. Less routine projects = more uncertainty in completion times. Uncertainty = limits usefulness in the CPM models.
What does CPM stand for?
Critical Path Method
