Project Time Management
Plan Schedule Management
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define policies, procedures and
documentation for managing and controlling project schedule
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including scheduling methodology,
tools, level of accuracy, control thresholds (limit beyond which
preventive/corrective actions needed), rules of performance measurement (e.g.
earned value)
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lead and lags are NOT schedule
constraints
Define Activities
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the scope baseline is used here as it
represents the approved (stable) scope
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further decompose work packages into
activities for more detailed and accurate estimations
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‘activities’ is the PMI terminology
for ‘tasks’ and ‘work efforts’
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activity is more related to the actual work/process to produce the
deliverables
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activity types: level of efforts
(support, measured in time period), discrete efforts or apportioned effort (in
direct proportion to another discrete effort)
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activities have durations while
milestones do not (zero duration)
Sequence Activities
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WBS is no longer needed, so the Project Scope Statement is the input rather than scope
baseline
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Precedence
Diagramming Method (PDM) to
diagram dependencies
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Network Diagramming Tools are
software tools that graphically represent activity sequences
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network diagrams: shows dependencies,
duration, workflow, helps identifying critical paths
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precedence
relationships (also known as ‘activity on node (AON)‘ approach): finish-to-start (~95%), start-to-start,
finish-to-finish, start-to-finish (least)
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Activity
on Arrow (AOA) or Arrow Diagramming Method (ADM) activities are represented as arrows,
dashed arrows represent dummy activities (duration: 0) that shows dependencies
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Graphical Evaluation and Review
Technique (GERT) allows for conditional branching and loops
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Network Dependency Types (to be
determined during Sequence Activities Process):
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Mandatory
Dependency (hard
logic): A must be completed before B begins/ technical dependencies may not be
hard
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Discretionary
Dependency (preferred,
soft logic): sequence preferred by the organization, may be removed should
fast-tracking is required
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External
Dependency: dependency required by external organization
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Internal
Dependency: precedence relationship usually within the project
team’s control
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Milestones:
the completion of a key deliverable/a phase in the project, as
checkpoints/summary for progress, often used in funding vendor activities
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Milestone list is part of i) project
plan, ii) project scope statement, iii) WBS dictionary
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Leads:
begin successor activity before end of predecessor, for schedule
compression (fast tracking) (negative lags)
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Lags:
imposed delay to successor activity, e.g. wait 2 weeks for concrete to cure (FS
+14 days)
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Network Diagram Setup : 7-box method, usually using software tools
or 5-box method
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if the ES and LS are identical, the
activity is on the critical path
Estimate Activity
Resources
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closely related to Estimate Cost
Process (in Cost Management)
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resource calendar spells out the
availability of resources (internal/external) during the project period
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matches human resources to activities
(as human resources will affect duration)
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effort (man
day, work week, etc.) vs duration vs time lapsed (total time needed, including
holidays, time off)
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alternative analysis includes
make-or-buy decisions, different tools, different skills, etc.
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Activity Resource Requirements may
include the basis of estimation
Estimate Activity
Durations
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consults SME (subject matter experts,
i.e. the one carrying out the actual work) to come with with the estimation,
not on the PM’s own
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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
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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
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One-Point Estimating: based on
expert judgement, but highly unreliable
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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
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In real world applications, the PERT
estimate is processed using Monte Carlo analysis, tie specific confidence
factors to the PERT estimate
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Bottom-Up Estimating:
a detailed estimate by decomposing the tasks and derive the estimates based on
reliable historical values, most accurate but time-consuming
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Heuristics:
use rule of thumb for estimating
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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%
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accuracy is
the conformance to target value
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contingency reserve:
for known unknowns, owned by PM, may be updated, part of schedule baseline
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management reserve:
for unknown unknowns, owned by management, included in overall schedule
requirements
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update to documents: basis of
estimates, assumptions and contingencies
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activity duration estimate may be in
a range, don’t
include lags
Develop Schedule
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the schedule baseline is the approved and signed version of
project schedule that is incorporated into the PM plan
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the schedule is calendar-based taking
into accounts holidays/resource availability/vacations
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vs the time estimate (work effort/level of effort) just
describes the man hours / man days
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Slack/Float: activities
that can be delayed without impacting the schedule
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Free slack/float: time an activity can be delayed without delaying the Early Start of the successor
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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
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Project Float: without affecting
another project
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Negative float:
problem with schedule, need schedule rework
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Project slack/float: time the project
can be delayed without delaying another project
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Early Start (ES) – earliest time
to start the activity
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Late Start (LS) – latest time to
start without impacting the late finish
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Early Finish (EF) – earliest time
to end the activity
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Late Finish (LF) – latest time to
finish without impacting successor activity
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Slack/Float = LS – ES or LF – EF
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The float is the highest single value
along the critical path, NOT the sum of them
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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)
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activities on the critical path are
called critical activities
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Path with negative float = behind schedule, need compression
to eliminate negative float
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Forward
Pass :
compute the early start
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Backward
Pass :
compute the late start
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Fast
Tracking :
allow overlapping of activities or activities in parallel, included
risks/resource overloading
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Crashing :
shorten the activities by adding resources, may result in team burnout
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Scheduling Techniques
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Critical
Path Method (CPM) –
compute the forward and backward pass to determine the critical path and float
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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)
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Buffer is determined by assessing the
amount of uncertainties, human factors, etc.
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Parkinson’s
Law: Work expands so as to fill the time available for
its completion.
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Resource Optimization Techniques
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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
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Resource
smoothing is
to adjust resource requirements so as not to exceed predetermined resource
limits, but only optimized within the float boundaries
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Modeling Techniques
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What
if analysis: to address feasibility/possibility of meeting project
schedule, useful in creating contingency plan
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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
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Network
Diagram: bar charts with logical connections
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Hammock activities:
higher-level summary activities between milestones
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Milestone
Charts: show only major deliverables/events on the timeline
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data date (status date, as-of date):
the date on which the data is recorded
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the Schedule Data includes schedule
milestones, schedule activities, activities attributes, and documentation of
all assumptions and constraints, alternative schedules and scheduling of
contingency reserves
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the Project Calendars identify
working days
Control Schedule
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measure result, make adjustments,
adjust metrics
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Performance Review includes: Trend
Analysis, CPM, CCM, Earned Value Management
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Change Requests generated are to be
assessed in the Perform Integrated Control Process
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