Let trust our estimates
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Transcript of Let trust our estimates
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: [email protected]
Thank You!
Copyright © 2011 SoftServe, Inc.
Skype: voytyshin