Project Management Project Time Management (Scheduling)

1. Project Management Project Time Management (Scheduling) Minder Chen, Ph.D. CSU Channel Islands Minder.chen@csuci.edu

2. Time • Limited time is the one constraint of any project with which we are all probably most familiar. • For many projects that create a product or event, time is the most important constraint to manage. • Project team members might not know the project budget or the scope of work in great detail, but chances are they all know the project deadline.

3. Sample Time Constraints • You are building a house and must finish the roof before the rainy season arrives. • You are assembling a large display booth for a trade show that starts in two months. • You are developing a new inventory-tracking system that must be tested and running by the start of the next fiscal year.

4. Project Time Management 6.1 Define Activities—The process of identifying the specific actions to be performed to produce the project deliverables. 6.2 Sequence Activities—The process of identifying and documenting relationships among the project activities. 6.3 Estimate Activity Resources—The process of estimating the type and quantities of material, people, equipment, or supplies required to perform each activity. 6.4 Estimate Activity Durations—The process of approximating the number of work periods needed to complete individual activities with estimated resources. 6.5 Develop Schedule—The process of analyzing activity sequences, durations, resource requirements, and schedule constraints to create the project schedule. 6.6 Control Schedule—The process of monitoring the status of the project to update project progress and managing changes to the schedule baseline.

5. ITTO for Scheduling Processes

7. Scheduling Overview

8. Examples of Project Schedules CPM: critical path method PERT: Project Evaluation & Review Technique Network Diagram Gantt Chart

9. Project Schedule—Graphic Examples • Milestone Schedule and Summary Schedule

10. Project Schedule—Graphic Examples

11. Precedence Diagramming Method • Visually easier to see precedence relationships • Ideal for large projects with many activities • They consist of a network of branches and nodes.

12. Developing the Project Plan • The Project Network is a diagram that graphically depicts the sequence, interdependencies, and start and finish times of the project job plan of activities (tasks). • Provides the basis for scheduling labor and equipment. • Enhances communication among project participants. • Provides an estimate of the project’s duration. • Provides a basis for budgeting cash flow. • Identifies activities that are critical. • Highlights activities that are “critical” and can not be delayed. • Help managers get and stay on plan.

13. Project Network Terminology • Activity: an element of the project that requires time. • Merge Activity: an activity that has two or more preceding activities on which it depends. • Parallel (Concurrent) Activities: Activities that can occur independently and, if desired, not at the same time. A B D C

14. Project Network Terminology • Path: a sequence of connected, dependent activities. • Critical path: the longest path through the activity network that allows for the completion of all project-related activities; the shortest expected time in which the entire project can be completed. Delays on the critical path will delay completion of the entire project. C B D A (Assumes that minimum of A + B > minimum of C + B in length of times to complete activities.)

15. Basic Rules to Follow in Developing Project Networks • Networks typically flow from left to right. • An activity cannot begin until all preceding connected activities are complete. • Arrows indicate precedence and flow and can cross over each other. • Each activity must have a unique identify number that is greater than any of its predecessor activities. • Looping is not allowed. • Conditional statements are not allowed. • Use common start and stop nodes.

16. Project Network Terminology • Event: a point in time when an activity is started or completed. It does not consume time. • Burst Activity: an activity that has more than one activity immediately following it (more than one dependency arrow flowing from it). • Two Approaches • Activity-on-Node (AON) • Uses a node to depict an activity. • Activity-on-Arrow (AOA) • Uses an arrow to depict an activity. • AON is the method used by most project management software packages. B C A D

17. Activity-on-Arrow (AOA) • Identify the critical path

18. Critical Path • Project Management Network Diagrams are helpful in determining where most of the schedule project risks will occur. • A critical path is made up of activities that cannot be delayed without delaying the end date of the project.

19. Create a List of Activity

20. Koll Business Center—Complete Network Sample List all activities and connect them based on their dependencies.

21. Koll Business Center—Complete Network 6-9 Indicate the duration (how many days) for each task.

22. Project Activity Notations The activity ID and name The normal duration time (DUR) The early start time (ES) The early finish time (EF) The late start time (LS) The late finish time (LF) The slack http://en.wikipedia.org/wiki/Critical_path_method

23. Network Computation Process • Forward Pass—Earliest Times • How soon can the activity start? (early start—ES) • How soon can the activity finish? (early finish—EF) • How soon can the project finish? (expected time—ET) • Backward Pass—Latest Times • How late can the activity start? (late start—LS) • How late can the activity finish? (late finish—LF) • Which activities represent the critical path? • How long can activity be delayed? (slack or float—SL)

24. Forward Pass: Earliest Time Start from day 0 How soon can the project finish? Early Start (ES) + Duration = Early Finish (EF) or Early Start (ES) + Duration – 1 = Early Finish (EF) ES of an activity = the largest EF of its immediately preceding activities

25. Forward Pass Computation • Add activity times along each path in the network (ES + Duration = EF). • Carry the early finish (EF) to the next activity where it becomes its early start (ES) unless… • The next succeeding activity is a merge activity, in which case the largest EF of all preceding activities is selected.

26. Backward Pass: Latest Time Latest day that the project should start Start here: The latest days that the project has to finish. Late Finish (LF) - Duration = Late Start (LS) or Early Start (ES) + Duration = Early Finish (EF) LF of an activity = the smallest LS of its immediately successsor activities

27. Backward Pass Computation • Subtract activity times along each path in the network (LF - Duration = LS). • Carry the late start (LS) to the next activity where it becomes its late finish (LF) unless… • The next succeeding activity is a burst activity, in which case the smallest LF of all preceding activities is selected.

28. Slack and Slippage • Now find the slack time (or 'float') for each task by subtracting the early start from the late start. SL (Slack) = LS – ES or SL (Slack) = LF – EF • The slack time is the amount of time the task can be slipped by without affecting the end date of the process. The critical path can now be identified as all paths through the network where the slack time is zero (The least slack time?). • Slippage: The amount of time that a task has been delayed from its original baseline plan. The slippage is the difference between the scheduled start or finish date for a task and the baseline start or finish date.

29. Backward Pass with Slack • Which path is the critical path? 165

30. Determining Free Slack (or Float) • Free Slack: how much a task can slip before it delays another task. • Is the amount of time an activity can be delayed after the start of a longer parallel activity or activities. • Is how long an activity can exceed its early finish date without affecting early start dates of any successor(s). • Allows flexibility in scheduling scarce resources. • Total slack is how much a task can slip before it delays the whole project. • Sensitivity • The likelihood the original critical path(s) will change once the project is initiated. • The critical path is the network path(s) that has (have) the least slack in common.

31. Critical Path Method (CPM) • In project management, a critical path is the sequence of project network activities which add up to the longest overall duration. • This determines the shortest time possible to complete the project. • Any delay of an activity on the critical path directly impacts the planned project completion date (i.e. there is no float on the critical path). • A project can have several, parallel, near critical paths.  http://en.wikipedia.org/wiki/Critical_path_method

32. Schedule Compression Techniques • Crashing: Shortening the durations of critical path activities by adding resources. Cost and schedule tradeoffs are analyzed to determine how to obtain the greatest amount of compression for the least incremental cost. • Fast tracking: Performing more activities in parallel. Phases or activities normally performed in sequence are performed in parallel. (e.g., laddering)

33. How to Create a Schedule from a Precedence Diagram

34. Critical Path Analysis • What tasks must be carried out. • Where parallel activity can be performed. • The shortest time in which you can complete a project. • Resources needed to execute a project. • The sequence of activities, scheduling and timings involved. • Task priorities. • The most efficient way of shortening time on urgent projects.

35. Critical Path Analysis • Regularly view the critical path(s). • Closely monitor critical tasks. • Review series of tasks that may become part of the critical path. • Protect yourself by viewing tasks that can slip without affecting the critical path.

36. PERT (Program Evaluation and Review Technique) • PERT is a variation on Critical Path Analysis that takes a slightly more skeptical view of time estimates made for each project stage. • To use it, estimate the shortest possible time each activity will take, the most likely length of time, and the longest time that might be taken if the activity takes longer than expected.

37. Three-Point Estimates

38. CPM vs. PERT • CPM or "Critical Path Method": • A single estimate for activity time was used that did not allow for variation in activity times • Activity times are assumed to be known or predictable ("deterministic") • PERT (Project Evaluation and Review Technique) • Multiple time estimates were used for each activity that allowed for variation in activity times • Activity times are assumed to be random, with assumed probability distribution ("probabilistic")

39. Practical Considerations • Network logic errors • Activity numbering • Use of computers to develop networks • Calendar dates • Multiple starts and multiple projects

40. PDM’s Four Types of Dependencies • Finish-to-start (FS). The initiation of the successor activity depends upon the completion of the predecessor activity. • Finish-to-finish (FF). The completion of the successor activity depends upon the completion of the predecessor activity. • Start-to-start (SS). The initiation of the successor activity depends upon the initiation of the predecessor activity. • Start-to-finish (SF). The completion of the successor activity depends upon the initiation of the predecessor activity.

41. Four Types of Dependencies • In PDM, finish-to-start is the most commonly used type of precedence relationship. • The start-to-finish relationship is rarely used but is included here for a complete list of the PDM relationship types.

42. Extended Network Techniques • Laddering (further decomposition) • Activities are broken into segments so the following activity can begin sooner and not delay the work. • Lags • The minimum amount of time a dependent activity must be delayed to begin or end. • Lengthy activities are broken down to reduce the delay in the start of successor activities. • Lags can be used to constrain finish-to-start, start-to-start, finish-to-finish, start-to-finish, or combination relationships.

43. Use of Lags Finish-to-Start Relationship Start-to-Start Relationship

44. Precedence Diagramming Method • The project management team determines the dependencies that may require a lead or a lag to accurately define the logical relationship. • A lead allows an acceleration of the successor activity. • A lag directs a delay in the successor activity.

45. Hammock Activities • An activity that spans over a segment of a project. Duration of hammock activities is determined after the network plan is drawn. • Hammock activities are used to aggregate sections of the project to facilitate getting the right amount of detail for specific sections of a project.

46. Develop Schedule: Tools and Techniques • Schedule Network Analysis • Critical Path Method • Critical Chain Method • Resource Leveling • What-if Scenario Analysis • Applying Leads and Lags / Laddering • Schedule Compression Techniques: • Fast tracking (i.e., performing more activities in parallel) • crashing the critical path (i.e., shortening the durations of critical path activities by adding resources).

47. Critical Chain Method • The resource-constrained critical path is known as the critical chain. The critical chain method adds duration buffers that are non-work schedule activities to manage uncertainty. One buffer, placed at the end of the critical chain, is known as the project buffer and protects the target finish date from slippage along the critical chain. Additional buffers, known as feeding buffers, are placed at each point that a chain of dependent tasks not on the critical chain feeds into the critical chain. • Feeding buffers thus protect the critical chain from slippage along the feeding chains. • The size of each buffer should account for the uncertainty in the duration of the chain of dependent tasks leading up to that buffer. Once the buffer schedule activities are determined, the planned activities are scheduled to their latest possible planned start and finish dates. • Consequently, in lieu of managing the total float of network paths, the critical chain method focuses on managing remaining buffer durations against the remaining durations of task chains. Ref: http://en.wikipedia.org/wiki/Critical_chain_project_management

48. Balancing The Triple Constraints in Projects

49. Key Terms Activity Activity-on-arrow (AOA) Activity-on-node (AON) Burst activity Concurrent engineering Critical path Early and late times Gantt chart Hammock activity Lag relationship Merge activity Network sensitivity Parallel activity Slack/float—total and free