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