Estimating Task Durations

Methodologies and Psychologyof Estimating

Project Schedules and Estimates

Accuracy at the task level translates up to the accuracy at the project level

Consistency is key

Estimating the unknownHow long does it take to catch a fish?Might be right awayMight be neverMight be anything in between

Estimating the unknownApply metrics to the madnessWhat is ‘most likely’ to happen?

Estimating the unknownWhat are the required ‘tools’ to complete the

task?Do we need to acquire the tools before

attempting the task?

Estimating the unknownMultiple tasks create an accumulation of

guesses‘Buffers’ 5+5=13

So what do we do? Buffers are not secretsEveryone knows durations are buffered

What Does the Task Duration Really Represent?

Discussion

Here are several approaches to estimating task durations:

Elapsed Time vs. Working TimeTask Time vs. Resource TimeInterface Losses & DelaysTheoretical Duration vs. Experience

Elapsed Time vs. Working Time

We don’t work ALL the time

Task Time vs. Resource Time

The number of people involved affects the elapsed time

Interface Losses & Delays How do we represent these spans of time to

accommodate ‘buffers’ / ‘losses’?

Theoretical Duration vs. Experience

What I know SHOULD happenvs.What I know Will happen

Here are a few traps to note:

Traps: MathImproper use of averaging

Trap: Skill Levels, Learning Curves & Priorities

Know your peopleKnow your priorities

Task Duration EstimationPERT Method

(a + 4b + c) / 6

PERT MethodDocument the estimation process

Delphi MethodWAG and SWAG

The Psychology of Task Durations

10 days to do 5 days of work. Why?

The Psychology of Task Durations

Work seems to expand if we have time for it

The Psychology of Task Durations

Do it tomorrow

The Psychology of Task Durations

Padding – we can’t seem to win either way

The Psychology of Task Durations

It seems for many it is natural to keep working until we are out of time or late

Practical Time EstimatingWe must pad or bufferWe must be realisticWhere’s the balance?

Practical Time EstimatingThere are methods that are tried and true

Practical Time EstimatingTechnique Example 1

Practical Time EstimatingTechnique Example 2

Practical Time EstimatingTechnique Example 3

Practical Time EstimatingTechnique Example 4

Develop consistency in estimating

Follow standards

Key factors in achieving project success

Know your objectives and these will drive your approach to Task Duration Estimations

Estimating Task DurationsStandardsDocumentationCommunication