Lecture Project management in practice (Fifth Edition) – Chapter 5: Scheduling the project. The following will be discussed in this chapter: Pert and CPM networks, project uncertainty and risk management, simulation, the gantt chart, extensions to PERT/CPM.
ProjectManagementinPractice FifthEdition Chapter5 SchedulingtheProject Copyrightâ2014JohnWiley&Sons,Inc 5ư1 Introduction ã ã ã Project schedule is the project plan in an altered format It is a convenient form for monitoring and controlling project activities Can be prepared in several formats – – – Gantt charts PERT network CPM network 52 PERT and CPM Networks • • PERT and CPM developed independently in 1950’s Program Evaluation and Review Technique (PERT) – – • U.S. Navy, BoozAllen Hamilton, and Lockheed Aircraft Probabilistic activity durations Critical Path Method (CPM) – – Dupont De Nemours Inc Deterministic activity durations 53 The Language of PERT/CPM • Activity – – • Event – – – • A task or set of tasks Uses resources and time An identifiable state resulting from completion of one or more activities Consumes no resources or time Predecessor activities must be completed Milestones – Identifiable and noteworthy events that mark significant progress 54 The Language of PERT/CPM Continued • Network – • Path – • A series of connected activities between two events Critical path – • A diagram of nodes (activities or events) and arrows (directional arcs) that illustrate the technological relationships of activities The set of activities on a path that, if delayed, will delay the completion date of the project Critical Time – The time required to complete all activities on the critical path 55 Building the Network • There are two ways of displaying a project network Activities on arrows (AOA) network • • Activities on nodes (AON) network • • • The activities are shown as arrows and events as nodes Generally more difficult to draw but depicts the technical relationships of the activities well Each task is shown as a node and the technological relationship is shown by the arrows AON network usually associated with CPM AOA network usually associated with PERT 56 Sample AON Network Table 51 Figure 53 57 Sample AOA Network Table 51 Figure 56 (a) 58 Which to Use? • • • Mostly AON used throughout this textbook AON used by most of the popular software AON networks are easier to draw by hand – • Large (20+ activities) AOA networks are difficult to draw Software to draw AOA networks is expensive 59 Finding the Critical Path and Critical Time • • • • • • • ES: Earliest start time EF: Earliest finish time LS: Latest start time LF: Latest finish time Displayed on node as shown ES + completion = EF LS + completion = LF Figure 59 510 The Probability of Completing the Project on Time Continued • • Determining the probability that a project is completed by a specified time requires calculating the probability that all paths are finished by the specified time We then calculate the probability that the entire project is completed within the specified time by multiplying these probabilities together – This requires the assumption that the paths are statistically independent 529 Calculating Path Probability • D = desired project completion Z time – • μ = the sum of the TE activities on the path being investigated – • • 50 in this example D 50 47 1.78 0.25 0.00 4.00 1.10 47 in this example σ2u = the variance of the path being considered A Z of 1.10 yields a probability of 0.8643 or 86 percent Table 54 530 The Statistical Distribution of the Completion Times for Example Figure 518 531 Selecting Risk and Finding D 532 Simulation • • • • Simulation is a different approach to managing risk Builds on the probabilistic functions already discussed Helps to understand the consequences of uncertainty Provides insight into the range and distribution of project completion times 533 Crystal Ball Chart for Project Completion Time Figure 519 534 Traditional Statistics vs. Simulation • • Both approaches assume that task times are statistically independent Both approaches assume the paths are independent – • A simulation can circumvent the assumption of statistical independence by including the activity or path dependencies as part of the model Simulation requires less computational effort 535 The Gantt Chart • • • Henry Gantt developed the Gantt chart around 1917 It displays project activities as bars measured against a horizontal time scale Most popular way of exhibiting sets of related activities in the form of schedules 536 The Chart • • Gantt charts are easy to draw Problems arise when several tasks begin at the same time and have the same duration – – • • Can make it hard to find critical path Only a problem on handdrawn charts Software shows critical path using some visual method Even with software, technical dependencies are harder to see on a Gantt chart 537 A Gantt Chart of a Sample Project Figure 521 538 A Gantt Chart Showing Critical Path, Path Connections, Other Data Figure 522 539 Extensions to PET/CPM • • • Application of fuzzy set theory to aid in estimating activity durations Extensions to precedence diagramming Goldratt’s Critical Chain 540 Precedence Diagramming • Finish to start (F to S) – • Start to start (S to S) – • Start of Activity A to start of Activity B Finish to finish (F to F) – • Finish of Activity A to start of Activity B Finish of Activity A to finish of Activity B Start to finish (S to F) – Start of Activity A to finish of Activity B 541 Precedence Diagramming Conventions Figure 525 542 Copyright Copyright © 2014 John Wiley & Sons, Inc All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make backup copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information herein 543 ... To complete a? ?project? ?by a specified time requires that all? ?the? ?paths? ?in? ?the? ?network be completed by? ?the? ?specified time 528 The? ?Probability of Completing? ?the? ? Project? ?on Time Continued • • Determining? ?the? ?probability that a? ?project? ?is ... Microsoft? ?Project? ?calculates using a calendar rather than days Uses a realworld calendar including weekends and holidays 527 The? ?Probability of Completing? ?the? ? Project? ?on Time • • Can? ?the? ?project? ?be completed? ?in? ?X days?...Introduction • • • Project? ?schedule is? ?the? ?project? ?plan? ?in? ?an altered format It is a convenient form for monitoring and controlling? ?project? ?activities Can be prepared? ?in? ?several formats – –