Project Time Management

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AIMS, UK

Project Time Management includes the processes required to accomplish timely completion of the project.

Activity Definition

Define Activities

the scope baseline is used here as it represents the approved (stable) scope
further decompose work packages into activities for more detailed and accurate estimations
‘activities’ is the PMI terminology for ‘tasks’ and ‘work efforts’
activity is more related to the actual work/process to produce the deliverables
activity types: level of efforts (support, measured in time period), discrete efforts or apportioned effort (in direct proportion to another discrete effort)
activities have durations while milestones do not (zero duration)

Activity Sequencing

Sequence Activities

WBS is no longer needed, so the Project Scope Statement is the input rather than scope baseline
Precedence Diagramming Method (PDM) to diagram dependencies
Network Diagramming Tools are software tools that graphically represent activity sequences
network diagrams: shows dependencies, duration, workflow, helps identifying critical paths
precedence relationships (also known as ‘activity on node (AON)‘ approach): finish-to-start (~95%), start-to-start, finish-to-finish, start-to-finish (least)
Activity on Arrow (AOA) or Arrow Diagramming Method (ADM) activities are represented as arrows, dashed arrows represent dummy activities (duration: 0) that shows dependencies
Graphical Evaluation and Review Technique (GERT) allows for conditional branching and loops
Network Dependency Types (to be determined during Sequence Activities Process):
Mandatory Dependency (hard logic): A must be completed before B begins/ technical dependencies may not be hard
Discretionary Dependency (preferred, soft logic): sequence preferred by the organization, may be removed should fast-tracking is required
External Dependency: dependency required by external organization
Internal Dependency: precedence relationship usually within the project team’s control
Milestones: the completion of a key deliverable/a phase in the project, as checkpoints/summary for progress, often used in funding vendor activities
Milestone list is part of i) project plan, ii) project scope statement, iii) WBS dictionary
Leads: begin successor activity before end of predecessor, for schedule compression (fast tracking) (negative lags)
Lags: imposed delay to successor activity, e.g. wait 2 weeks for concrete to cure (FS +14 days)
Network Diagram Setup : 7-box method, usually using software tools or 5-box method
if the ES and LS are identical, the activity is on the critical path

Activity Resource Estimating

closely related to Estimate Cost Process (in Cost Management)
resource calendar spells out the availability of resources (internal/external) during the project period
matches human resources to activities (as human resources will affect duration)
effort (man day, work week, etc.) vs duration vs time lapsed (total time needed, including holidays, time off)
alternative analysis includes make-or-buy decisions, different tools, different skills, etc.
Activity Resource Requirements may include the basis of estimation

Activity Duration Estimating

Consult subject matter experts, i.e. the one carrying out the actual work to come with with the estimation.  PM should not make them on his own when data is not available. If data is available, statistical techniques can be used.

Analogous Estimating: based on previous activity with similar nature (a form of expert judgement), used when little is known or very similar scope, works well when project is small, NOT ACCURATE

Parametric Estimating: based on some parameters, e.g. the time for producing 1000 component based on that for 1 component * 1000, use an algorithm based on historical data, accuracy depends on the parameters selected, can be used on [a portion of / the entire] project

One-Point Estimating: based on expert judgement, but highly unreliable

Three-Point Estimating: best (optimistic), most likely (realistic), worst (pessimistic) cases,

Triangular Distribution vs PERT (Project Evaluation and Review Techniques, Beta Distribution, weighted average using statistical methods [most likely * 4 – 95% confidence level with 2 sigma]), triangular distribution (non-weighted average of three data points), uncertainties are accounted for
In real world applications, the PERT estimate is processed using Monte Carlo analysis, tie specific confidence factors to the PERT estimate

Bottom-Up Estimating: a detailed estimate by decomposing the tasks and derive the estimates based on reliable historical values, most accurate but time-consuming

Heuristics: use rule of thumb for estimating
standard deviation (sigma value, deviation from mean, to specify the precision of measurement): 1 sigma: 68%, 2 sigma 95%, 3 sigma 99.7%, 6 sigma 99.99%
accuracy is the conformance to target value
contingency reserve: for known unknowns, owned by PM, may be updated, part of schedule baseline
management reserve: for unknown unknowns, owned by management, included in overall schedule requirements

Update to documents: basis of estimates, assumptions and contingencies

Activity duration estimate may be in a range, don’t include lags

Schedule Development

The schedule baseline is the approved and signed version of project schedule that is incorporated into the PM plan
the schedule is calendar-based taking into accounts holidays/resource availability/vacations
vs the time estimate (work effort/level of effort) just describes the man hours / man days


Slack/Float: activities that can be delayed without impacting the schedule
Free slack/float: time an activity can be delayed without delaying the Early Start of the successor
Total slack/float: time an activity can be delayed from early start without delaying the project end date (scheduling flexibility), can be negative, 0 (on the critical path) or positive
Project Float: without affecting another project
Negative float: problem with schedule, need schedule rework
Project slack/float: time the project can be delayed without delaying another project
Early Start (ES) – earliest time to start the activity
Late Start (LS) – latest time to start without impacting the late finish
Early Finish (EF) – earliest time to end the activity
Late Finish (LF) – latest time to finish without impacting successor activity
Slack/Float = LS – ES or LF – EF
The float is the highest single value along the critical path, NOT the sum of them

Critical Path: the longest path that amount to shortest possible completion time (usually zero float, activities with mandatory dependency with finish-to-start relationship), can have more than 1 critical paths (more risks), critical paths may change (keep an eye on near-critical paths)
activities on the critical path are called critical activities
Path with negative float = behind schedule, need compression to eliminate negative float
Forward Pass : compute the early start
Backward Pass : compute the late start
Fast Tracking : allow overlapping of activities or activities in parallel, included risks/resource overloading
Crashing : shorten the activities by adding resources, may result in team burnout

Scheduling Techniques

Critical Path Method (CPM) – compute the forward and backward pass to determine the critical path and float
Critical Chain Method (CCM) – deal with scarce resources and uncertainties, keep the resources levelly loaded by chaining all activities and grouping the contingency and put at the end as project buffer, for activities running in parallel, the contingency is called feeding buffer (expect 50% of activities to overrun)
Buffer is determined by assessing the amount of uncertainties, human factors, etc.
Parkinson’s Law: Work expands so as to fill the time available for its completion.
Resource Optimization Techniques
Resource leveling is used to adjust the variation in resource loading to stabilize the number of resources working each time and to avoid burnout, may need to extend the schedule in CPM
Resource smoothing is to adjust resource requirements so as not to exceed predetermined resource limits, but only optimized within the float boundaries

Modeling Techniques

What if analysis: to address feasibility/possibility of meeting project schedule, useful in creating contingency plan
Monte Carlo: run thousand of times to obtain the distribution using a set of random variables (stochastic variables), use a combination of PERT estimate and triangular distributions as end point estimates to create the model to eliminate schedule risks, the graph is a ‘S’ curve
Network Diagram: bar charts with logical connections
Hammock activities: higher-level summary activities between milestones
Milestone Charts: show only major deliverables/events on the timeline
data date (status date, as-of date): the date on which the data is recorded
the Schedule Data includes schedule milestones, schedule activities, activities attributes, and documentation of all assumptions and constraints, alternative schedules and scheduling of contingency reserves
The Project Calendars identify working days

 Schedule Control

Measuring results, making adjustments,
Adjust metrics
Performance Review includes: Trend Analysis, CPM, CCM, Earned Value Management
Change Requests generated are to be assessed in the Perform Integrated Control Process

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