Project Time Management
Ashima Wadhwa
Schedule Development
– Determining start and finish dates for project
activities
– Without realistic dates, project unlikely to be
finished as scheduled
– Schedule development process often iterates as
more information becomes available (process
inputs)
Schedule Development Inputs:
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Project Network Diagram
Activity Duration Estimates
Resource Requirements
Resource Pool Description – availability patterns; shared
resources are highly variable
– Calendars – define eligible work periods
• Project Calendars affect all resources
• Resource Calendars – affect specific resource pools or individuals
Schedule Development Inputs (continued):
– Constraints
• Imposed Dates – may be required
• Key events or milestones – are initially requested and become
expected during project
– Assumptions
– Lead and Lag Time – dependencies may specify time in
order to satisfy relationship (example – 2 weeks to receive
order)
Schedule Development Tools &
Techniques
• Mathematical Analysis
• Monte Carlo Analysis
Mathematical Analysis
– Mathematical Analysis – calculating theoretical early/late
finish and start dates without regard for resource pool
limitations; indicate time periods which activity should be
scheduled given resource limits and other constraints:
• Critical Path Method (CPM) – single early/late start and finish date for all activities.
Based on specified, sequential network and single duration estimate. Calculates
float to determine flexibility
• Graphical Evaluation and Review Technique (GERT) – probabilistic treatment of
network and activity duration estimates
• Program Evaluation and Review Technique (PERT)- sequential network and
weighted average duration to calculate project duration – differs from CPM by
using mean (expected value) instead of most-likely estimate in CPM
Mathematical Analysis
– Critical Path Method: refers to estimating based on one time estimate
per activity
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One time estimate per task (Most Likely)
Emphasis on controlling cost and leaving schedule flexible
Drawn using AOA diagrams
Can have dummy task
– PERT (Program Review and Estimating Technique)
• 3 Time estimates per activity
– Optimistic
– Pessimistic
– Most Likely
• Emphasis on meeting schedule, flexibility with costs
• Drawn on AOA diagrams
• Can have dummy tasks
Monte Carlo Analysis
– Monte Carlo Analysis
• Uses a computer with PERT values and network diagram
• Tells
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Probability of completing a project on any specific day
Probability of completing a project for any specific amount of cost
Probability of any task actually being on the critical path
Overall Project Risk
• Suggests that Monte Carlo simulation will create a project duration
that is closer to reality than CPM or PERT
Schedule Development Tools & Techniques
• Schedule Development Tools & Techniques
(continued)
– Duration Compression – look to shorten project schedule
without affecting scope
• Crashing – cost and schedule trade-offs to determine greatest
amount of compression for least incremental cost – often results
in higher costs
• Fast Tracking – performing activities in parallel that normally
would be sequenced – often results in re-work and usually
increases risk
– Simulation
Schedule Development Tools & Techniques
• Schedule Development Tools & Techniques
(continued)
– Resource Leveling Heuristics – leveling resources that
apply to critical path activities a.k.a. “resource constrained
scheduling” – when limitation on quantity of available
resources; sometimes called “Resource Based Method” –
often increases project duration
– Project Management Software
Chapter 6 – Project Time Management
• Schedule Development Tools & Techniques (continued)
– Project Manger’s role
• Provide the team with the necessary information to properly estimate the
task
• Complete a sanity check of the estimate
• Formulate a reserve
– Project Team should be involved; determine task estimates
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Historical Records
Guesses
Actual Costs
Benchmarks
CPM and PERT
Critical Path Method:
– Critical Path Method: longest path through a
network diagram and determines the earliest
completion of the project
– Proves how long the project will take
– Indicates tasks that need most monitoring
– Almost always have no slack
Schedule Development Outputs:
– Project Schedule – includes planned start and finish dates
for each activity; remains preliminary until resources
assignments are approved. Usually in following formats:
• Project Network Diagrams (with date information added) – show
logical and critical path activities
• Bar or Gantt charts – activity start and end dates, expected
durations
• Milestone Charts – identifies key deliverables and interfaces
• Time-scaled network diagrams – blend of project network and bar
charts
Chapter 6 – Project Time Management
• Schedule Development Outputs (continued):
– Supporting Detail – all assumptions and constraints. May
also include:
• Resource requirement by time period (resource histogram)
• Alternative schedules (best/worst case)
• Schedule reserve/risk assessments
– Schedule Management Plan – how updates are managed
– Resource requirement updates – leveling and activity
impact
Chapter 6 – Project Time Management
• Schedule Control:
– Influencing factors which create schedule changes to
ensure changes are beneficial
– Determining that schedule has changed
– Managing actual changes as they occur
• Inputs to Schedule Control
– Project Schedule – baseline approved, measure against
project performance
– Performance Reports – planned dates met, issues
– Change Requests
– Schedule Management Plan
Chapter 6 – Project Time Management
• Schedule Control Tools & Techniques
– Schedule Change Control System – defines
procedures for schedule changes, paperwork,
approval, tracking systems
– Performance Measurement – assess magnitude of
variations to baseline; determine if corrective
action is needed
– Additional Planning
– Project Management Software
Schedule Control Outputs:
– Schedule Updates – any modifications,
stakeholder notification
• Revisions change scheduled start and finish dates –
generally in response to scope changes. “Rebaselining” may be needed in drastic situations
– Corrective Action – re-align performance with
project plan
– Lessons Learned
Chapter 6 – Project Time Management
• Key knowledge points not in PMBOK
– Need to know manual calculations of network
diagrams
• Created after project charter and WBS (task estimates
and dependencies are determined)
– Mandatory dependencies (Hard Logic) – inherent in nature of
work
– Discretionary dependencies (Soft Logic) – based on
experience, desire or results
– External dependencies – based on needs and desires of
organizations outside the project
Chapter 6 – Project Time Management
• Methods to draw network diagrams
– Activity on Node (AON) or Precedence Diagramming
Method (PDM)
• Boxes represent tasks
• Arrows show task dependencies
• 4 types of task relationships
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Finish to Start (task must finish before next can start)
Finish to Finish (task must finish before next can finish)
Start to Start (task must start before next can start)
Start to Finish (task must start before the next can finish)
• No dummy tasks used
Chapter 6 – Project Time Management
• Methods to draw network diagrams
– Activity on Arrow (AOA or Arrow Diagramming Method
(ADM)
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Arrows used to represent tasks
Only Finish to Start relationships are used
May use dummy tasks (show dependencies)
PERT and CPM estimating techniques can only be drawn using AOA
– CPM (Critical Path Method) – estimating based on one time estimate
per activity (the most likely time estimate)
» Emphasizes controlling cost and allowing schedule flexibility
» Can have dummy tasks
Chapter 6 – Project Time Management
• Methods to draw network diagrams
– Activity on Arrow (AOA or Arrow Diagramming
Method (ADM) continued:
• PERT (Program Evaluation and Review technique)
– 3 time estimates per activity: Optimistic (O), Most Likely (M),
Pessimistic (P)
– Emphasizes meeting schedule, flexibility with cost
– Can have dummy tasks
Chapter 6 – Project Time Management
• Methods to draw network diagrams
– PERT (Program Evaluation and Review technique)
– Estimating based on 3 formulas:
• PERT Duration: (P + 4M + O)/6
• Standard Task Deviation: (P – O)/6
• Task Variance:
[P – O]2
• Total project estimate:
6
– Add up all Optimistic, Most Likely and Pessimistic values of the critical path
tasks and apply P + 4M + O/6
• Total project variance (+/-):
– Add up the individual task variances and take the square root of the value.
Use the value as a +/- figure to compute the Optimistic and Pessimistic values.
The total project estimate will serve as the basis.
Chapter 6 – Project Time Management
• Monte Carlo Simulation:
– Uses a computer with PERT values (P, M, O) and a network
diagram but does not use the PERT formula
– Indicates
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Probability of completing project on a specific day
Probability of completing project for any specific amount of cost
Probability of any task actually being on critical path
Overall project risk
Chapter 6 – Project Time Management
• Estimating techniques in general:
– Should be performed by entire project team
• Project manager needs to provide information to allow team to
create estimates; sanity check; formulate reserve
– Estimates are:
• Guesses, Historical Records, Actual Costs, Benchmarks, CPM, PERT
– Critical paths determines the earliest completion date and identifies
tasks that need monitoring
– Can be obtained by CPM, PERT and Monte Carlo estimating
techniques
Chapter 6 – Project Time Management
• Key Definitions:
– Slack (Float): the amount of time a task can be delayed
without delaying the entire project. Tasks on critical path
have no slack.
• Slack is calculated by the difference between Early Start and Late
Start of a task
– Free Slack (Float): the amount of time a task can be delayed without
delaying the early start date of its successor
– Total Slack (Float): the amount of time a task can be delayed without
delaying the project completion date
– Lag: inserted waiting time between tasks
Chapter 6 – Project Time Management
• General Comments:
– Projects can have more than 1 critical path (increases risk) and can
involve dummy tasks
– Negative float indicates that you are behind
– Resource Leveling involves possibly letting schedule and cost slip
– Heuristics – just means “rule of thumb” e.g. 80/20 rule
– Schedules are calendar based – makes this different than a time
estimate
• Bar Chart a.k.a. Gantt chart (track progress, report to entire team
including stakeholders, control tool)
• Network Diagram (to show task inter-dependencies, show project
organization, basis for project control)
• Milestone chart (report to Senior management, shows major events)
• General Comments:
– To shorten project schedule examine the critical
path
• Crashing – add more resources to the critical path tasks
– Usually results in increased cost
• Fast Tracking – performing tasks in parallel
– Can result in re-work and increased risk
– Best to select method that has least impact on the
project (is the importance on cost, risk or
schedule?)
Chapter 6 – Project Time Management
• General Comments:
– Bar (Gantt) Charts
• Weak Planning Tool, effective progress and reporting tool
• Does not show interdependencies of tasks
• Does not help organize the project more effectively
– Network Diagrams (PERT, CPM, PDM)
• Shows task interdependencies
• Aids in effectively planning and organizing work
• Provides a basis for project control
– Milestone Charts
• Only shows major events
• Good for reporting to management and customer
– Flow Charts
• Depicts workflow and not commonly used for project management
Chapter 6 – Project Time Management
• General Comments:
– Free Slack (Float) – amount of time a task can be delayed without delaying the early
start date of its successor
– Total Slack (Float) – amount of time a task can be delayed without delaying the project
completion date
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Lag – inserted waiting time between tasks
Resource Leveling – level peaks of resource usage; stable number of resources –
allows schedule and cost slip in favor of leveling resources
Heuristic – rule of thumb (80/20 rule)