Volodymyr Voytyshyn

02/19/2012

Let Trust Your Estimates

� Have you ever estimated development tasks before start work on them?

� How accurate were your estimates?� How accurate were your estimates?

� What did you do when you underestimated or overestimated the task?

� Have you ever estimated whole project before its start?

The Goal

How makeestimate of software project efforts

BETTER?

Main Points

� Why Good Estimate is Important?

� Some Anti-Patterns in Projects Estimation

� Estimation Approaches Overview� Estimation Approaches Overview

� PERT in Action

WHY GOOD ESTIMATEIS IMPORTANT?

What is successful software project?

� All main requirements were implemented

� No time overhead

� No budget overhead

� No overtimes

Software Project Statistics

32%24%

CHAOS Summary 2009

44%

Failed

Challenged

Successed

http://www.standishgroup.com/newsroom/chaos_2009.php

What is the main problem?

When do we need estimates?

� Preparation of proposal for a new project

� Project planning

� Managing changes

� Managing risks

� Etc…

Why estimate is important?

Bad

Estimate

Unsuccessful

Project

Underestimation Consequences

� Demotivation

� Low Quality

� Increase Growth of Costs

� Etc…

SOME ANTI-PATTERNSIN PROJECTS ESTIMATION

Anti-Pattern #1

� Estimate something when anybody do not know what is this

Anti-Pattern #2

� Talk “Yes” when you actually think “No”

Anti-Pattern #3

� Forcible reducing of estimate

Anti-Pattern #4

� Excessive optimism

Anti-Pattern #5

� Make hasty estimates

Anti-Pattern #6

� Software project includes only coding

Anti-Pattern #7

� Not consider risks

ESTIMATION APPROACHES OVERVIEW

What is an estimate?

� Estimate is a probability value

� What is the confidence range?

� What is the probability that we’ll exceed the estimate?

Estimation Approaches

� Your own experience in similar projects

� Expert’s estimation:– PERT, Program / Project Evaluation and

Review TechniqueReview Technique

� General techniques based on industry experience:– FPA, Functional Point Analysis

– COCOMO, Constructive Cost Model

PERT

� PERT - Program / Project Evaluation and Review Technique

� The technique was designed at 1958 during project on the creation of missiles "Polaris"project on the creation of missiles "Polaris"

� Input data: hierarchical structure of project tasks

� Output data: probabilistic estimation of efforts

PERT: Calculations

PERT: Calculations

PERT: Calculations

Functional Point Analysis

� Was designed by Alan Albrecht and first published at 1979

� Input data: logical model and requirements for software projectsoftware project

� Output data: functional points

� Main benefit: unified and platform independent approach for estimation all projects in company

COCOMO

� COCOMO – constructive cost model

� Was designed by Barry Bouem and first published at 1981

� Input data: KLOC – thousands of logical code lines

� Output data: effort estimate in man-month

PERT IN ACTION

Task

� Automated ordering system for company which specializing on wholesale trade

� Customer should be able to create an order

� Manager should be able process an order

� Email notification for all steps of order workflow

� 1C synchronization

Estimation

Result

Conclusion

A. Underestimate has very negative impact on project

B. Software project estimation is not a guessing

C. We can use and combine several estimation approaches:

– Experience on similar projects

– PERT

– FPA

– COCOMO

Ask your question…

Information Sources

� Software Project Management Lectureshttp://www.arkhipenkov.ru

� 10 Deadly Sins of Software Estimationhttp://construx.com/Page.aspx?cid=2929http://construx.com/Page.aspx?cid=2929

� Software Estimation: Demystifying the Black Arthttp://www.microsoft.com/learning/en/us/book.aspx?ID=2425&locale=en-us

Contacts

Volodymyr Voytyshyn

5 Knyahyni Olhy Str., Rivne 33000, Ukraine

Tel: +38(066) 41 83 509

E-mail: vvoit@softserveinc.com

voytyshyn@gmail.com

Thank You!

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Skype: voytyshin