Software Estimation Technique

Wideband Delphi Technique

George Ukkuru

Introduction

Consensus based approach for estimation

Developed in the 1940’s at Rand

Corporation

Team of experts prepare individual

estimates.

Benefits

Build a complete task list or work breakdown structure for major activities.Consensus approach helps eliminate bias in estimates.Eliminate hidden agendas or divergent objectives for inexperienced estimators or influential individuals.Does not require historical data to prepare the estimates.

Straightforward and Repeatable process

Process

Planning

Project Manager selects a team and a moderatorTeam consists of 3-7 team membersRepresentation from all groups like development, testing etcModerator to be familiar with the Delphi processIdeal to have the Project Manager as a part of estimation teamProject Manager should not be the moderator as he will have stake in the outcome of the estimation

Kickoff Meeting

Explain the Delphi process

Read the vision and scope document or any

supporting documents [Pre-requisites]

Review the goals of the estimation session

Brainstorm and note down the assumptions

Generate the initial WBS

Decide upon the unit for estimation

Individual Estimation

Estimate the time required for each task

Add any additional tasks to the WBS

Add any missing assumptions

Estimation Meeting

Moderator shares the estimates so that estimators can see the range of estimatesIndividual estimates are not sharedTeam members revises estimates based on group discussionsEstimates are revised until no estimator wants to changes his/her estimates.Estimators agree that the estimates are acceptable.

Wide Band Delphi Example

There estimators A,B and C are told to prepare the time required to prepare test scenarios for a projectThe initial estimations provided were

A – 18 Hours B – 38 Hours C – 58 Hours

The moderator then Calculates average estimate as 38 hoursReturns this with their original estimates to

the estimators

Wide Band Delphi Example

The estimators then meet and discuss the estimates The initial estimations provided were

A – 31 Hours B – 32 Hours C – 33 Hours

The moderator then Calculates average estimate as 32 hoursAsks the estimators if they agree with this as

the estimate

Iterations in Estimations

Round 2                                  X X X    

Round 1   X   X   X

  10 20 30 40 50 60

Assemble Tasks & Review Results

Project Manager works with the team and collects the estimates from team membersCompiles the final WBS, estimations and assumptionsReviews the final estimates with the estimation team

Ground Rules

All estimation sessions must be performed individually with no group interaction Estimators must indicate factors affecting their estimatesEstimators will ignore holidays, vacations and other similar factors Anonymity must be observed during the whole estimation process Estimation sessions should have a predefined time limit

Assumptions

Assume that one person will perform all

tasks

Assume all tasks will be performed

sequentially

Assume that you can devote

uninterrupted time to each task

About the Author George Ukkuru is working as a test manager with

UST Global Trivandrum. He is having more than 10 years of experience in the field of software testing. He holds various certifications like PMP,CAPM,CSTE etc. He can be reached at [email protected]