Software Estimation Slide 1

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Software Estimation

Demystifying the Black Art

by

Steve McConnell

Presented by

Lee Bennett, PMP

Software Estimation Slide 2

Definition of Estimating

• DeMarco– [The common definition of an estimate is]

“the most optimistic prediction that has a non-zero probability of coming true.” …the earliest date by which you can’t prove you won’t be finished.

• McConnell– … provides a clear enough view of the

project to allow … good decisions about how to control the project to hit its targets.

Software Estimation Slide 3

Software Estimation

• Author: Steve McConnell– Code Complete (1993, 2004)– Rapid Application Development (1996)– Software Project Survival Guide (1998)

Software Estimation Slide 4

Cone of Uncertainty

Software Estimation Slide 5

Estimating Techniques

• T Shirt sizing

• Software Estimation tools

• Wideband Delphi

• Story Points

Software Estimation Slide 6

T Shirt Sizing

• Technique– Estimate S/M/L Business Value– Estimate S/M/L Development Cost– Go with the low hanging fruit

• Applicability– Very early in project

• Results– Doesn’t actually produce an estimate– Eliminates the need to estimate some

cases

Software Estimation Slide 7

Estimation Tools

• Technique– Simulation– Probability analysis– www.construx.com

• Applicability– Early to middle for medium to large

projects

• Results– Can produce highly accurate results*

Software Estimation Slide 8

Wideband Delphi

• Technique– A structured group estimating technique– Basis of Agiletek’s estimating– Anonymous estimates

• Applicability– Early in medium to large projects

• Results– 40% improvement over initial group

average– Meeting time is expensive

Software Estimation Slide 9

Story Points

• Technique– Give each story a size estimate from the

Fibonacci sequence (1,2,3,5,8,13…)– Deliver some stories in an N week iteration– Velocity = [Story Points delivered] / N weeks– Duration = [Total Story Points] / Velocity

• Applicability– Early to Middle stage

• Example– http://www.planningpoker.com/

Software Estimation Slide 10

Project Planning and Control

Estimating is a skill of project planning.

Planning determines appropriate Commitments.

Project Controls are needed to help meet Commitments.

Software Estimation Slide 11

Questions ???

Software Estimation Slide 12

Estimating Concepts

• Use multiple estimating techniques– Estimate by analogy, top down– Estimate by components, bottom up

• Estimate size first– Scheduling estimates only after effort

estimate is in place