BASICS OF CPM & PERTTOOLS FOR

PROJECT MANAGEMENT

CPM: A NETWORK ANALYSIS TECHNIQUE USED TO PREDICT PROJECT DURATION BY ANALYSING WHICH SEQUENCE OF ACTIVITIES HAS THE LEAST AMOUNT OF SCHEDULING FLEXIBILITY (LEAST FLOAT). EARLY DATES ARE CALCULATED BY FORWARD PASS USING A SPECIFIED START DATE. LATE DATES ARE CALCULATED BY MEANS OF A BACKWARD PASS STARTING FROM A SPECIFIED COMPLETION DATE (PROJECTS EARLY FINISH DATE )

PERT: PROGRAM EVALUATION & REVIEW TECHNIQUE: AN EVENT ORIENTED NETWORK ANALYSIS TECHNIQUE USED TO ESTIMATE PROJECT DURATION WHEN THERE IS HIGH DEGREE OF UNCERTAINTY WITH INDIVIDUAL ACTIVITY DURATION ESTIMATES.

PHASES OF PROJECT MANAGEMENTPLANNINGSCHEDULING CONTROLLING

Importance of Planning

For want of a nail, the shoe was lost,For want of a shoe, the horse was lost,For want of a horse, the rider was lost,For want of a rider, the battle was lost,For want of a battle, the kingdom was lost,And all for want of a horse-shoe nail.

If man does not know to what port he is steering, no wind is favourable to him

PLANNINGSetting the objectives of the project and the assumptions to be made.SWOT Analysis.Development of Work Breakdown Structure (W.B.S.)Estimating the activity durations, their resources requirements and costs.Establishing the interdependence relationships between the activities.

SCHEDULINGStart and finish times for each activity

Critical path on which the activities require special attention

Slack and float for the non-critical paths.

CONTROLLINGMake periodical progress reports.

Reviewing the progress.

Analysing the status of the project.

Management decisions regarding updating, crashing and resource allocation

NETWORK LOGIC & TERMINOLOGYActivity: It is a physically identifiable part of a project which consumes time and resources. Activities are obtained by the work breakdown into smaller work contents.Event: The beginning and end points of an activity are called events or nodes. Event is a point in time and does not consume any resources. Activityij

PATH: An unbroken chain of activities connecting the initial event to some other event is called a path.

NETWORK: It is graphical representation of logically and sequentially connected arrows and nodes representing activities and events of a project. Networks are also called arrow diagrams.

NETWORK CONSTRUCTIONFirstly the project is split into activities.

Start and end events of the project are then decided.

After deciding the precedence order, the activities are put in a logical sequence by using graphical notations.

Logical sequence checked through:What activities must be completed before a particular activity starts?What activities follow this?What activities must be performed concurrently with this?

Predecessor Activities: Activities which must be completed before a particular activity starts.Successor Activities: Activities which must follow a particular activity

Time flows from left to right . Arrows pointing in opposite directionare to be avoided.Dummy: An activity which only determines the dependency of one activity over the other, but does not consume any time is called a dummy activity.Partial Dependency: In certain situations the starting of an activity depends upon the partial completion of a predecessor activity. In such cases the predecessor activityis further broken into two parts and dummy is used to make the connection.Looping and dangling cases are not permitted.

CPM is deterministic in nature and activity oriented with single time estimate.PERT is probabilistic in Nature and event oriented with three time estimates.TIME ESTIMATES:OPTIMISTIC TIME ESTIMATE (to): The shortest possible time required for the completion of an activity, if all goes extremely well.PESSIMISTIC TIME ESTIMATE (tp): The maximum possible time the activity will take if everything goes bad.MOST LIKELY TIME ESTIMATE (tm): It is the time an activity will take if executed under normal conditions.

SOME PROBABILITY RELATIONSMean,(u) : (to + 4tm+tp) / 6

Standard deviation, : ( tp-to)/6

2Varience,(V) : (tp-to/6)

Expected time = Mean

CRITICAL PATHThe path which takes place the maximum of time is called the critical path and activities on the critical path are called critical activities.The Critical path calculation consists of: Forward Pass Calculations & Backward Pass Calculations.

CRITICAL PATH INTRACANCIES: IN A PROJECT NETWORK THE SERIES OF ACTIVITIES WHICH DETERMINES THE EARLIEST COMPLETION OF THE PROJECT. CRITICAL PATH WILL GENERALLY CHANGE FROM TIME TO TIME AS ACTIVITIES ARE COMPLETED AHEAD OF OR BEHIND SCHEDULE. ALTHOUGH NORMALLY CALCULATED FOR ENTIRE PROJECT , CRITICAL PATH CAN ALSO BE DETERMINED FOR A MILESTONE OR SUBPROJECT. THERE CAN BE MORE THAN ONE CRITICAL PATHS IN A NETWORK. CRITICAL PATH IS USUALLY DEFINED AS THOSE ACTIVITIES WITH FLOAT LESS THAN OR EQUAL TO A SPECIFIED VALUE OFTEN ZERO.

Activity on Arrow: Activity and duration of the activity are shown in arrow The Critical Path for this network is: A-B-C-D-I-J. The events on the critical path have zero slack. Dummy activity has no duration The total duration for the completion of the project is 110 days based on the critical path.