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Sins of Estimation

Decent Essays

10 Deadly Sins of Software Estimation
Steve McConnell
© 2002 Construx Software Builders, Inc. All Rights Reserved. www.construx.com

D e l e ring Softw are P e ct Succe ss iv roj

Construx

®

Background

Estimation Book v Construx Estimate™ v Construx’ Training s v Construx’ Consulting s v www.construx.com

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Art and Science of Software Estimation
Science of estimation is well-developed and well-supported by software tools v Art of estimation relies on rules of thumb and still needs some work v 3

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Almost-Deadly Sins of Software Estimation Sins #20-#11

Sin #20

Estimating how long “it” …show more content…

are developers tend to be introverts and relatively young v Marketing and sales personnel tend to be more extroverted and organizationally senior to the developers they negotiate with v 21

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Sin #3 Committing to Estimates Too Early in the Cone of Uncertainty

The Cone of Uncertainty
Project cost (effort and size) 4x Project schedule

Most estimates are created here

2x 1.5x 1.25x 1.0x 0.8x 0.67x 0.5x

Good estimates aren’ t possible until here

1.6x

1.25x 1.15x 1.1x 1.0x 0.9x 0.85x 0.8x

0.25x

0.6x

Time
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Plan to Revise Estimates Throughout the Project
Project cost (effort and size) 4x Project schedule 1.6x

2x 1.5x 1.25x 1.0x 0.8x 0.67x 0.5x

1.25x 1.15x 1.1x 1.0x 0.9x 0.85x 0.8x

0.25x

0.6x

Suitable only as estimates

Suitable as estimates Time and commitments

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Sin #4 Assuming Underestimation has No Impact on Project Results

Effect of Estimation Accuracy
Non-linear impact due to planning errors, upstream defects, high-risk practices

Cost Effort Schedule

Linear impact due to Parkinson’ Law s

Underestimation

Overestimation

< 100%

100%

>100%

Target as a Percentage of Nominal Estimate
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Sin #5 Estimating in the “Impossible Zone”

Puzzle

Suppose

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