Time Management Week 7 - Learning Objectives
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Time Management Week 7 - Learning Objectives
You should be able to: List and describe the processes, activities,
inputs, and outputs in time management Create and interpret a network diagram Create and interpret a GANTT chart Define and use: CPM, critical path and time,
slack time, crash time, fast-tracking
Time Management Issues
Frequent source of project failure– Often used as a success measure
Frequent source of project conflict Time / cost / scope tradeoffs Less negotiable, least flexibility Stakeholder involvement
– communication and commitment
Time Management Processes Define Activities
– further defines scope
Sequence Activities– further defines time
Estimate Duration– further defines cost
Develop Schedule Control Schedule
Activity
Element of work - on WBS– cost– duration– resources
“Tasks” vs. “activities”? – Doesn’t matter, as long as the work to be
done is described accurately and understood by those who must do the work
Define Activities
Steps needed to produce deliverables Inputs:
– WBS, Scope, historical data, constraints, assumptions
Outputs: – Activity list, descriptions, supporting detail,
updates to WBS– complete understanding of work involved
Sequencing Activities
Identifying dependencies– relationships between activities
Mandatory dependencies– technical, defined by type of work
Discretionary dependencies– defined by project team
External dependencies– relationships to non-project activities
Activity Sequencing Tools
Network diagrams – schematic display of activities and
dependencies– activity on arrow (AOA or ADM)
Precedence diagramming – activity on node (AON or PDM)
1
5
73
4
62
A (20)
C (10)
I (18)
F (14)
E (10)
J (8)
D (15)
B (20)
G (4)
H (11)
Precedence Diagram (PDM)
Boxes represent activities Types of dependencies:
– finish-to-start– start-to-start (can be parallel)– finish-to-finish (can be parallel)– start-to-finish (rarely used)
Estimating Duration Should involve stakeholders, people doing the
work Inputs:
– Activity list, constraints, assumptions
– Resource requirements
– Resource capabilities (human and materials)
– Use historical data, previous projects, experience, simulations
Outputs: duration estimates– quantitative assessments of likely number of work
periods required to complete activity
Developing the Schedule
Inputs to schedule development:– project network diagram– activity duration estimates– resource requirements– resource pool description– calendars (project and resource)– constraints, assumptions, leads and lags
Scheduling Tools
GANTT charts CPM: Critical Path Method PERT: probabilistic time estimation Simulation
GANTT Chart
shows planned vs. actual progress multiple tasks on horizontal time scale easy to read, easy to construct monitoring and control of progress requires frequent updating limited display of dependencies
Components of GANTT Chart
Activities - scheduled and actual Precedence relationships Milestones (identifiable points in project)
– usually represents reporting requirements
– usually corresponds to critical events Can add budget information Does not show technical interdependencies Need network diagram to interpret, control, and
compensate for delays
Gantt Chart symbols
Milestone: – diamond
Summary task: – dark bar
Individual task: – light bar
Arrows: – dependencies
CPM Definitions
Activity: uses resources and takes time
Event: result of completing an activity
– has identifiable end state at a point in time
Network: combined activities & events in a project
Path: series of connected activities Critical: activities, events, or paths which, if delayed, will
delay project completion Critical path: sequence of critical activities from start to
finish Node: start or end of an activity Arrow (Arc): shows path
Task Precedence Time
a - 5 daysb - 4 daysc a 6 daysd b 2 dayse b 5 daysf c,d 8 days
A,52
3
4
B,4 E,5
F,8
C,6
D,2 51
A-C-F = 19
B-E = 9
B-D-F = 14
Critical Path is
A-C-F
Critical Time 19
EOT: – earliest occurrence time for event
– time required for longest path leading to event
LOT: latest occurrence time for event EST: earliest starting time for activity LST: latest starting time for activity Critical time: shortest time in which the
project can be completed Slack time: difference between earliest and
latest start times
1
5
73
4
62
A (22)
C (10)
I (18)
F (14)
E (10)
J (8)
D (15)
B (20)
G (4)
H (11)
Event LOT EOT Slack
1 0 0 02 20 20 03 21 20 14 14 10 45 25 24 16 35 35 07 43 43 0
Activity LST EST Slack PredecessorDuration
a 0 0 0 - 22b 1 0 1 - 20c 4 0 4 - 10d 20 20 0 a 14e 25 20 5 b,c 8f 29 20 9 b,c 14g 21 20 1 b,c 4h 14 10 4 c 12I 25 24 1 g,h 16j 35 35 0 d,e 8
What is the critical path? Critical time?– B-F = 34– B-E-J = 38– A-D-J =– B-G-I =– C-H-I =
What is the earliest occurrence time of event 6?
What is the latest start time for activity F?
Probabilistic Time Estimation More realistic, includes uncertainty Expected completion time
– optimistic, pessimistic, most likely times take weighted average of the 3 times
TE = (a + 4m + b)/6
uncertainty = variance (range of values) Probability of completion of project in
desired time DZ = (D - ì)/(sqrt(ó2
ì))
D = completion timeActivity a m b TE VarianceStd Dev a = optimistic
b = pessimistica 10 22 22 20.000 4.000 2.000 m = most likelyb 20 20 20 20.000 0.000 0.000c 4 10 16 10.000 4.000 2.000 TE = (1x a) + (4 x m) + (1 x b)d 2 14 32 15.000 25.000 5.000 Var = ((TE - m) / 6) squarede 8 8 20 10.000 4.000 2.000 Std = Sqrt(Var)f 8 14 20 14.000 4.000 2.000g 4 4 4 4.000 0.000 0.000 Z = (D - sum(TE))/(sqrt(sum Var))h 2 12 16 11.000 5.444 2.333 for activities on critical pathI 6 16 38 18.000 28.444 5.333j 2 8 14 8.000 4.000 2.000
43.000 5.745D = 43 Critical Path = a-d-j
45 Critical Time = 43 days50
Outputs of Scheduling Process
Date-enhanced project network diagram GANTT charts, milestone charts Time-scaled network diagrams
– combines GANTT, network diagram Supporting detail Schedule management plan
Shortening the Schedule
Duration compression Crashing:
– time/cost tradeoff Fast tracking:
– parallel vs. sequential Resource loading and leveling:
– more even distribution of resource usage
Activity PrecedenceDuration Cost Crash -- Normal Cost per
Normal Crash Normal Crash Duration Cost Period
a - 3 2 $40 80 -1 $40 ($40)
b a 2 1 20 80 -1 $60 ($60)
c a 2 2 20 20 -- --
d a 4 1 30 120 -3 $90 ($30)
e b 3 1 10 80 -2 $70 ($35)
Critical Path is: a-b-eCritical Time is: 8 periods
Slope = (crash cost - normal cost ) (crash time - normal time) = cost per day of crashing activity
Schedule Control Determining, managing schedule changes Influencing changes so they are beneficial Inputs:
– schedule, performance reports, change requests, schedule management plan
Outputs:– schedule updates & notification– corrective action to minimize delays– lessons learned
Controlling Schedule Changes Involve stakeholders
– manage expectations– progress meetings – no surprises
Leadership, discipline, negotiation– review draft schedule and add details– realistic estimates– allow for contingencies– empower and incent employees
Proper use of tools