CPM-: Principles of Schedule Management Lesson B: Critical Path Scheduling Techniques Instructor Jim Wrisley IPM Fall Conference PMI-College of Performance Management Professional Education Program Copyright All Rights Reserved
Lesson Objectives - TLO #: The student will understand the evolution of network scheduling, be able to differentiate between two () primary types of network scheduling methods and understand the value of resource loading the network. ELO #: The student will recognize the evolution of PERT Scheduling. ELO #: The student will be able to recognize and the Precedence Diagramming Method (PDM) type schedule. ELO #: The student will recognize the value of resource loading a schedule. Copyright All Rights Reserved
Lesson Objective - TLO #: The student will understand how to create and analyze a PDM type schedule. ELO #: The student will be able to recognize and use the PERT Formula for calculating durations. ELO #: The student will be able to define the use of : Finish-to-Start, Start-to-Start, Finish-to-Finish, relationships. ELO #: The student will be able to define and calculate: critical path, and total float on a PDM Schedule. Copyright All Rights Reserved
Lesson Outline Reviewing History of Network Scheduling PERT Durations Present Three Major Types of Network Schedule Estimating Techniques and Associated Terminologies Demonstrate Network Computations Discuss the Importance of Resource Leveling Discussion Copyright All Rights Reserved
Network Scheduling Copyright All Rights Reserved
The History of Network Scheduling PERT Scheduling U.S. Navy Special Projects Office Polaris Missile Program 9 Critical Path Method Remington-Rand and Dupont Chemical processing 9 - Activity-on-Node (AON) also known as Precedence Diagramming Method (PDM) --- Most Popular - Activity-on-Arrow (AOA) also known as Arrow Diagramming Method (ADM) Copyright All Rights Reserved
Critical Path Method (CPM) Estimating Method An Activity receives a Single Point Estimate instead of the required by PERT. Hence no formula is needed. Example: Estimated Duration = days Copyright All Rights Reserved
Program Evaluation Review Techniques (PERT) Estimating Method The PERT Formula Uses a Point Estimate Pessimistic + xmost Likely + Optimistic Given: P = days M= days O = days + + = =. Copyright All Rights Reserved
Monte Carlo Simulations Estimating Method Monte Carlo Simulations uses PERT s Point Estimates as basis. But it does not use the PERT formula. This statistical technique utilizes a computer to simulate the outcome of a project. It will give you the probability of completing the project on any given day! Copyright All Rights Reserved
Pros and Cons of Estimating Methods CPM: Easiest to use. Many experts believe it is the least accurate predictor. PERT: More sophisticated and requires more thought. Many experts believe it is more accurate than CPM. Monte Carlo Simulations: Most sophisticated. Many experts believe it is the best prediction technique Copyright All Rights Reserved 9
Basic Scheduling Terms Critical Path: Longest path through Project. Has no slack. Slack (Float): The amount of time an activity can be delayed without delaying the project. Lag: Inserted waiting time between tasks. Estimating Methods: (CPM, PERT, Monte Carlo) Resource Leveling: Allows a more stable number of resources to be used on the project. Crashing The Schedule: Adding more resources to the Critical Path Fast Tracking: Doing more tasks in parallel. Copyright All Rights Reserved
The Goals Of Project Management: to make the most effective use of available resources such as: People Equipment Facilities Materials Money Technology so that project objectives and goals can be achieved: Within budget On schedule To the desired quality Copyright All Rights Reserved
WBS Work Packages / Activities CONTROL ACCOUNT WORK PACKAGES ACTIVITIES Copyright All Rights Reserved
CALCULATING THE NETWORK Task Durations Forward Pass Backward Pass Copyright All Rights Reserved
Task Durations (Estimates) Developed for each activity Developed by best available authority Generally assumes normal conditions (manpower, equipment, calendar, etc.) CAUTION: - Over- Estimating Tendencies Copyright All Rights Reserved
Activity Types DURATION DRIVEN Estimate based on amount of calendar time necessary for task completion EFFORT DRIVEN Estimate based on the amount of work required to complete the activity Copyright All Rights Reserved
PDM Network - A H L A D M/S I J K M/S Project Start B E Project Completed C F G M PROJECT LENGTH? Copyright All Rights Reserved
Forward Pass From project start to finish, calculate the earliest that each activity can start and finish according to the logical sequence of work and the duration of each activity EARLY DATES Yields project duration Copyright All Rights Reserved
PDM Network - A A D H L 9 9 M/S Project Start B E I J K M/S 9 Project Completed C 9 9 F G M FORWARD PASS Copyright All Rights Reserved
Backward Pass Working backward from project finish to start, calculate the latest that each task must start and finish in order to meet the end date. LATE DATES Yields when the project must start to meet the latest acceptable completion date. Copyright All Rights Reserved 9
PDM Network - A A D M/S Project B E Start H 9 9 I J L 9 K 9 M/S 9 Project Completed 9 9 9 C F G M 9 9 BACKWARD PASS Copyright All Rights Reserved
Why Calculate The Network? Establish ES & EF dates and project duration Calculate LF & LS dates based on project completion Defines Float Copyright All Rights Reserved
Float (Leeway Or Slack) Amount of time an activity can be delayed before it impacts Project Completion Calculated by comparing LF to EF A = days "Float" Also called Total/Path/Shared Float Copyright All Rights Reserved
Total Float ES EF 9 A A Total Float for Activity A LS LF Copyright All Rights Reserved
Activity (Free) Float Amount of time an activity can be delayed before it impacts any succeeding activity days "Free Float" D H Copyright All Rights Reserved
PDM Network - A A D M/S Project B E Start H 9 9 I J L 9 K 9 M/S 9 Project Completed 9 9 9 C F G M 9 9 Critical Path Copyright All Rights Reserved
Critical Path Longest path of logically related activities through the network which has the least Total Float. Defines project duration. Path: B E G M + + + = 9 days Copyright All Rights Reserved
Resource Leveling Copyright All Rights Reserved
Why We Resource Load Networks Assignment of resources (people, equipment, facilities, materials, etc.) to each activity within the project Comparison of Needs vs. Availability Resulting Profiles (Histograms) Cumulative Plots (S-Curves) Other descriptive terms: Resource Allocation Resource Leveling Resource Scheduling Resource Smoothing Copyright All Rights Reserved
We Develop A Staffing Plan Because... During Critical Path Method (CPM) schedule development, the assumption has been that unlimited manpower, material and equipment are available This OFTEN is not true The availability of resources has a direct bearing on the duration of each activity. Copyright All Rights Reserved 9
CONTROL ACCOUNT $ $ $ $ $ $ $ $ $ $ $ $ $ Total $ $ $ $ $ $ $ $ $ Automated? Manual? Hrs Hrs Hrs Hrs Hrs Hrs Hrs Hrs Copyright All Rights Reserved
Resources-loaded Schedules Schedules that have required resources identified to a specific schedule activity ACTIVITY X TITLE: Review Geology Report EARLY START LATE START / / EARLY FINISH LATE FINISH / / DURATION: days TF = Resources: Hydrogeologist Hydrogeologist Assistant Hours Copyright All Rights Reserved
PDM Network - A May May May May May May A May 9 May D H May Jun L Jun Jun May May May 9 May May May 9 May May May May May M/S Project Start May May B May May May May E May May I May May J Jun Jun K Jun Jun Jun M/S Project Completed May May May May May May 9 May Jun C F G M May May May May May May 9 May Jun Copyright All Rights Reserved
Network A Activity Duration Total Float Free Float Resources A B C D E F G H* I J K L M *Duration Driven Copyright All Rights Reserved
Copyright All Rights Reserved Activity A B C D E F G H I J K L M 9 9 ( = Late Finish) May June
Total Resources by Day - Net A Net A Resource Profile Resource Requirements 9 9 9 Project Days Copyright All Rights Reserved
Why We Do Resource Analysis Determine resource requirements (manpower projections, hire/fire strategies) Balance resource usage Consider time/resource tradeoff Copyright All Rights Reserved
Total Float ES EF 9 A A Total Float for Activity A LS LF Copyright All Rights Reserved
Copyright All Rights Reserved Activity A B C D E F G H I J K L M 9 9 ( = Late Finish) May June
PDM Network - A A D M/S Project B E Start H 9 9 I J L 9 K 9 M/S 9 Project Completed 9 9 9 C F G M 9 9 Critical Path Copyright All Rights Reserved 9
May June Activity 9 9 Total Float A B C D E F G H I J K L LOGIC A "DRIVES" D D "DRIVES" H - L - I - J - K M ( = Late Finish) Copyright All Rights Reserved
"Net A" Resource Profile Resource Requirements 9 9 9 Project Days Copyright All Rights Reserved
S Curves R E S O U R C E S TIME-PHASED RESOURCE PLAN (CUMULATIVE PLOT) TIME Copyright All Rights Reserved
Copyright All Rights Reserved ( = Late Finish) May June Activity A B C D E F G H I J K L M 9 9
"Net A" Resource Curves Cumulative Resources Early Start Late Start Scheduled (Baseline) 9 9 9 Project Days Copyright All Rights Reserved
FORECASTING RESOURCES A E G B C D F H A B C D E F RESOURCES G H TOTAL CUM 9 9 9 9 USAGE TABLE R E S O U R C E S Copyright All Rights Reserved TIME PROFILE CUMULATIVE (S) CURVE
Should I Resource Load My Schedule? Pros: Tight integration of schedules and budgets Visibility of resource requirements by skill category Facilitates enterprise-wide resource planning Ease of what if modeling during the planning phase Facilitates recovery planning Cons: Requires expert scheduling capabilities (software & personnel) Over reliance on software tools instead of resource managers Some resources are more critical than others Benefits diminished if not done on an enterprise-wide basis Copyright All Rights Reserved
Planning & Budgeting Establish the Baseline - An Iterative -Step Process. Define The Work Project Budget Base Mgmt Res. Schedule The Work $ Baseline. Allocate Resources Time Copyright All Rights Reserved
Additional Reading Resources Scheduling Guide for Program Managers: Defense Acquisition University - A Guide To Project Management Body of Knowledge: Project Management Institute- PMP Exam Prep- nd Edition: Rita Mulcahy, PMP Copyright All Rights Reserved
Copyright All Rights Reserved 9