PROJECT MANAGEMENT CPM/PERT V P B Chakravarthi . K Abhijeet Kumar
CPM and PERT CPM (Critical Path Method) and PERT (Program Evaluation and Review Technique) are network based methods designed to assist in the planning, scheduling, and control of projects. A project is a collection of interrelated activities with each activity consuming time and resources. The objective of CPM and PERT is to provide analytic means for scheduling the activities.
Terms Used in Project ManagementActivity : A certain amount of work or task required in the projectActivity duration: In CPM the best estimate of time to complete an activity . In PERT the expected time or average time to complete an activityCritical activity : An activity that has no room for schedule slippages : if it slips the entire the entire project completion will slip. An activity with zero slack
Terms Used in Project Management .cont Critical path: The chain of critical activities for the project .The longest path through the network Dummy activity :An activity that consumes no time but shows precedence among activities Earliest finish (EF): The earliest that an activity can finish from the beginning of the project Earliest start ( ES): The earliest that an activity can start from the beginning of the project
Terms Used in Project Management .cont Event :A beginning , a completion point ,or a milestone accomplishment within the project . An activity begins and ends with events Latest finish (LF) : The latest that an activity can finish from the beginning of the project Latest start (LS) :The latest that an activity can start from the beginning of the project
Terms Used in Project Management .cont Predecessor activity : An activity that must occur before another activity . Slack : The amount of time that an activity or group of activities can slip without causing a delay in the completion of the project Successor activity : An activity that must occur after another activity
Terms Used in Project Management .contConventions used in drawing network diagrams (Arrows & Circles ) Activity on Arrow (AOA) : The activities are denoted by Arrows and events are denoted by circles Activity on Node(AON) : Activities are denoted by circles(or nodes) and the precedence relation ships between
Network planning methods that generate:♦ Relationship between activities♦ Project duration♦ Critical path♦ Slack for non – critical activities♦ Crashing (cost / time trade-offs)♦ Resource usage
Project “Aproject is a series of activities directed to accomplishment of a desired objective.” Plan your work first…..then work your plan
Network analysisIntroductionNetwork analysis is the general name given to certain specifictechniques which can be used for the planning, management andcontrol of projects.One definition of a project:“A project is a temporary endeavour undertaken to create a "unique"product or service”
Developed in 1950’s History CPM by DuPont for chemical plants PERT by U.S. Navy for Polaris missileCPM was developed by Du Pont and the emphasis was on thetrade-off between the cost of the project and its overallcompletion time (e.g. for certain activities it may be possibleto decrease their completion times by spending more money -how does this affect the overall completion time of theproject?)PERT was developed by the US Navy for the planning and control ofthe Polaris missile program and the emphasis was on completing theprogram in the shortest possible time. In addition PERT had theability to cope with uncertain activity completion times (e.g. for aparticular activity the most likely completion time is 4 weeks but itcould be anywhere between 3 weeks and 8 weeks).
CPM - Critical Path Method Definition: In CPM activities are shown as a network of precedence relationships using activity-on-node network construction – Single estimate of activity time – Deterministic activity times USED IN : Production management - for the jobs of repetitive in nature where the activity time estimates can be predicted with considerable certainty due to the existence of past experience.
PERT - Project Evaluation & Review Techniques Definition: In PERT activities are shown as a network of precedence relationships using activity-on-arrow network construction – Multiple time estimates – Probabilistic activity times USED IN : Project management - for non-repetitive jobs (research and development work), where the time and cost estimates tend to be quite uncertain. This technique uses probabilistic time estimates.
Gantt chart Originated by H.L.Gantt in 1918Advantages Limitations- Gantt charts are quite commonly used. - Do not clearly indicate details regardingThey provide an easy graphical the progress of activitiesrepresentation of when activities (might)take place. - Do not give a clear indication of interrelation ship between the separate activities
CPM/PERTThese deficiencies can be eliminated to a large extent by showing the interdependence of various activities by means of connecting arrows called network technique. Overtime CPM and PERT became one technique ADVANTAGES: – Precedence relationships – large projects – more efficient
The Project Network Use of nodes and arrows Arrows An arrow leads from tail to head directionally – Indicate ACTIVITY, a time consuming effort that is required to perform a part of the work. Nodes A node is represented by a circle - Indicate EVENT, a point in time where one or more activities start and/or finish.
Activity on Node & Activity on ArrowActivity on Node Activity on Arrow- A completion of an activity - An arrow represents a task, is represented by a node while a node is the completion of a task - Arrows represent order of events
Activity SlackEach event has two important times associated with it :- Earliest time , Te , which is a calendar time when a event can occur when all the predecessor events completed at the earliest possible times- Latest time , TL , which is the latest time the event can occur with out delaying the subsequent events and completion of project. Difference between the latest time and the earliest time of an event is the slack time for that eventPositive slack : Slack is the amount of time an event can be delayed without delaying the project completion
Critical Path Is that the sequence of activities and events where there is no “slack” i.e.. Zero slack Longest path through a network minimum project completion time
Benefits of CPM/PERT Useful at many stages of project management Mathematically simple Give critical path and slack time Provide project documentation Useful in monitoring costs