Lecture 10

• Project schedule limitations

  • Logical order in which activities need to be completed
  • How long each activity will take
  • How many key resources are available at specific points in the project
  • Imposed dates
  • Cash flow
• Potential problems in estimating time accurately

  • Logical order in which activities need to be completed
  • How long each activity will take
  • How many key resources are available at specific points in the project
  • Imposed dates
  • Cash flow
• Use the activity on node (AON) method to develop a project schedule


  1. Identify all activities

  2. Determine logical order

  3. Assign resources to each activity

  4. Estimate time required for that activity

  5. Compare schedule with imposed dates

  6. Consider project budget and cash flow, quality demands, and risk factors
• Activity

  A distinct, scheduled portion of work performed during the course of a project
• Activities

  • Clear start and end
  • Tangible output
  • Controlled scope
  • Labor, costs, schedule controlled
  • Single person accountability
• Plan Schedule Management

  Building blocks of a project schedule are activities
• Project time management processes

  • Plan schedule management
  • Define activities
  • Sequence activities
  • Estimate activity resources
  • Estimate activity durations
  • Develop schedule
  • Control schedule
• Purposes of a Project Schedule

  • When will the project be complete?
  • What is the earliest a particular activity can start, and when will it end?
  • What activity must begin before which other activities can take place?
  • What would happen if a delivery of material was one week late?
  • Can a key worker take a week vacation the first week of March?
  • If one worker is assigned to do two activities, which one must go first?
  • How many hours do we need from each worker next week or month?
  • Which worker or other resource is a bottleneck, limiting the speed of our project?
  • What will the impact be if the client wants to add another module?
  • If I am willing to spend an extra $10,000, how much faster can the project be completed?
  • Are all of the activities completed that should be by now?
• Historical Development of Project Schedules

  • Scheduling as a result of competition
  • Program Evaluation and Review Technique (PERT) and Critical Path Method (CPM) – 1950s
  • Identify activities
  • Determine their logical order
  • Estimate the duration of each activity
• Critical Path Method (CPM)


  A method used to estimate the minimum project duration and determine the amount of scheduling flexibility on the logical network paths within the schedule model
• PERT

  • Estimate most likely time needed to complete a project
  • Estimate level of confidence in completing a project in a particular time
  • Useful in (R&D) projects
• CPM

  • Used to plan very large projects
  • Used single time estimates for each activity
  • Focus on longest sequence of activities
  • Used to determine how to complete a project early
  • Useful in the construction industry
• Activity on Node (AON) or Precedence Diagramming Method (PDM)


  • Most widely used
  • Scheduled activities are represented by nodes and are graphically linked by one or more logical relationships to show the sequence in which the activities are performed
• Predecessor activity

  An activity that logically comes before a dependent activity in a schedule
• Successor activity

  A dependent activity that logically comes after another activity in a schedule
• Mandatory dependency

  A relationship that is contractually required or inherent in the nature of the work
• Discretionary dependency

  A relationship that is established based on knowledge of best practices where a specific sequence is desired
• Finish-to-start (FS) dependency


  The most common type of logical relationship where a successor activity cannot start until a predecessor activity has finished
• Lead

  The amount of time whereby a successor activity can be advanced with respect to a predecessor activity
• Lag

  The amount of time whereby a successor activity is required to be delayed with respect to a predecessor activity
• Finish-to-finish

  A logical relationship in which a successor activity cannot finish until a predecessor activity has finished
• Start-to-start

  A logical relationship in which a successor activity cannot start until a predecessor activity has started
• Start-to-finish

  A logical relationship in which a successor activity cannot finish until a predecessor activity has started
• Duration

  The total number of work periods (not including holidays or other non-work periods) required to complete a schedule activity, usually expressed as workdays or workweeks
• Don't omit activities, as activity sequencing may uncover missing activities
• Avoid adding activities after the final schedule is approved
• Use previous projects, templates, or checklists as a starting point when defining activities
• Project Milestones

  • Completion of a major deliverable
  • Completion of a critical activity
  • Prior to a large financial commitment
  • Merging point in the project schedule
• The schedule will not be approved until all related planning is in place
• Estimate Activity Duration

  • Evaluate each activity independently
  • Document all assumptions and constraints
  • Changing assumptions and constraints could change estimates
• Verify all time estimations with the people doing the work
• Estimate times of completion of work without initial reference to a calendar
• Make sure all time units are identical: working days, work week, months (consider time off for company holidays)
• Factors to consider for realistic time estimates

  • Inaccuracy in work instructions
  • Unexpected meetings
  • Learning curves
  • Interruptions
  • Emergencies/illness
  • Vacation
  • Resources or information not available on time
  • Rework
• Acknowledge tendency toward optimistic or pessimistic estimations
• First establish a realistic estimate
• Adjust estimates based on size, familiarity, and complexity differences
• Learning Curves

  The more times a person performs an activity, the better and faster he or she becomes
• Factors affecting rate of improvement in learning curves

  • How much the culture of the organization stresses continual improvement
  • How much of the activity is dependent on the worker versus dictated by the pace of a machine
  • How much skill is involved in the activity
  • How complex that activity is
• Time calculated based upon a rate of improvement