CP2730 - Chapter 4 Schedule Planning 1. Activity definition leads to the WBS Activity definition should not be so tight as to define virtually every task.

CP2730 - Chapter 4

Schedule Planning

1

Activity definition leads to the WBS

Activity definition should not be so tight as to define virtually every task

The activity definition process goes just far enough to identify all tasks so you can create time and budget estimates

Defining Activities

2

Activity Sequencing

Some activities can run side by side

Others must occur one before the other – these activities are said to have dependencies

Types of dependencies: Mandatory: one task depends on another Discretionary: you can choose the sequence

and/or dependency of a task(s) External: something outside affects/controls

the task’s sequencing (dependency)

3

Logical Relationships

One task can affect the start/finish time of another, it may need to be finished before another starts: Predecessor: a task that occurs before another

task (on the same path) Successor: a task that occurs after another task (on

the same path)

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Task B

(B is a successor to

task A)

Task A

(A is a predecessor to

task B)

Logical RelationshipsDifferent kinds of relationships can exist between

activities: Finish- to-Start: successor cannot begin until

predecessor finishes Start-to-Finish: finish of successor depends on

start of predecessor Finish-to-Finish: finish of successor depends on

finish of predecessor Start-to-Start: start of successor depends on start

of predecessor

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A network diagram models project activities and the relationships among the activities.

The Precedence Diagramming Method (PDM) is a common type of network diagram (see next slide).

PDM style uses boxes to represent tasks and arrows to show dependencies.

Creating a Network Diagram

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Creating a Network Diagram

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Network Diagram (PDM) Example

In this example (taken from Figure 4.2 in text): Activity A is a predecessor to Activities B and D. Activity B is a predecessor to Activities C and D. In order for D to start, both A and B must be complete. In order to end the project, both C and D must be

complete.

B EndA C

D

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Start

Basic rules for PDM network diagrams: there is one start and one end box each box equates to one activity (task) arrows connect one box to another an arrow coming into a box indicates a dependency there can be more than one arrow coming out of or

going into a box (indicating multiple dependencies) network diagrams are created after activity

estimates are known

Creating a Network Diagram

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Activity Duration EstimatingAlong with identifying tasks (activities) and their dependencies,

you need to specify (estimate) how long each task takes.

Duration is how long it takes to complete a task in terms of days, hours, weeks, months, etc. – the total elapsed time.

When estimating how long an activity is going to take, hours in the workday, weekends, holidays, etc. have to be considered.

* See Figure 4.3

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Duration Estimating TechniquesSeveral techniques can be used for estimating,

including: analogous: using durations from similar

activities on a previous project expert judgement: using experts to create

estimates – someone who can draw on past experience

parametric estimating: quantitatively based where the quantity of work multiplied

by the rate

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Duration Estimating Techniques three-point estimates: an average of the “most likely”

estimate, “pessimistic” estimate and “optimistic” estimate

sample: (10 + 16 + 7)/3 = 11 days

PERT (Program Evaluation and Review Technique): similar to “three-point” but use 4 of the “most likely” in your

calcs and divide by 6 to get the average

sample: ((10*4) + 16 + 7)/6 = 10.5 days

* See Figure 4.4

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Creating The Project ScheduleSchedule development is the establishment of start

and finish dates for all project activities

Schedule development techniques include: Mathematical analysis (critical path method) Duration compression Project management software

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Critical Path Method (CPM)The Critical Path Method:

the longest activity sequence path in the project controls the finish date of the project activities on path have no float (slack) time also identifies tasks that can start late (have float

time)

To use CPM, complete the following steps:1. Forward Pass2. Backward Pass3. Float

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CPM Forward Pass

Use Network Diagram and working from left-to-right:

1. Calculate Early Start: Earliest date activity may begin based on any predecessors 1st task has Early Start of 0 Use duration of activity (plus any predecessors)

2. Calculate Early Finish: Earliest date activity may finish based on Early Start Use duration of activity (plus Early Start)

* See Figure 4.4 and Table 4.1

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CPM Backward PassUse Network Diagram and working from right-to-left:

1. Calculate Late Finish: Latest date activity may complete without impacting end date Late Finish of last task(s) is the project finish date Subtract duration from Late Finish to get Late Finish of its

predecessor

2. Calculate Late Start: Latest date activity may be started without impacting end date Late Start of 1st task is 0 Subtract duration from Late Finish to get Late Start Late Start of one task becomes Late Finish for its predecessor

* See Figure 4.4 and Table 4.2

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CPM Float

Using the Forward Pass and/or Backward Pass information, calculate Float by either:

subtracting Early Start from Late Start subtracting Early Finish from Late Finish

* NOTE: If done correctly, using either calculation will give the same result, so you can verify correctness by doing both.

* See Figure 4.4 and Table 4.3

The Critical Path includes all tasks that do not have Float (slack) time.

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Duration CompressionDuration Compression can be used when total project time is

calculated to be greater than expected completion time

Compression techniques include: Crashing:

You add resources to an activity so as to reduce its duration You cannot crash critical path activities Might result in a new critical path May have an economic impact on project (can be costly to do)

Fast Track: Do tasks in parallel (that would normally be done in sequence) Involves a lot of risk, so must communicate this to stakeholders

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Project Management SoftwareProject Management Software (such as MS Project) can

be very useful in scheduling, WBS, etc. and in communicating this info.

Various diagrams and charts can be created and used (i.e. Gantt, etc.)

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Project Management SoftwareMilestones are key events in a project:

which should be identified/defined which often involve major deliverables whose dates are very important that can be documented using a milestone chart

(* see Table 4.4) Gantt charts can also show milestones

(* see Figure 4.5 for a sample Gantt)

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Project Management SoftwareThe schedule baseline is the:

final approved version of schedule (at the start of project)

must be approved by stakeholders can be used throughout project to measure

progress should only be changed if (absolutely) necessary

* See page 106 (Real World Scenario) for discussion of some of the Chaptal Wineries project scheduling, etc. issues 21