4.9 MODIFIED DELPHI TECHNIQUE

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4.9 MODIFIED DELPHI TECHNIQUE

The Modified Delphi technique is a way of eliciting and reconciling the opinions of a group of individuals. It can be used, as can all of these techniques except the use of models, to derive cost or size estimates. Because it relies on opinion it can be used at any time during the development lifecycle, but I feel it is best used from initiation to the end of high level design.

The first thing the primary estimator should do is form an estimating group consisting of themselves and at least two other assistant estimators. One individual should be nominated as the Coordinator. In reality, these groups usually exist permanently within product groups and are activated as necessary. In this way they act as good training grounds for estimators. The group should not exceed seven individuals even for large projects as larger groups often become unmanageable.

Next, each group member is given access to any material about the new project, typically this will be a customer request document or a requirements specification.

They should be given sufficient time to study this material bearing in mind their other work and, typically, we are talking about a week of elapsed time. They should also be notified of a date when a reconciliation meeting will be held.

Each group member makes their estimate and submits these to the Coordinator at least two days before the reconciliation meeting. The Coordinator calculates the median or mid-point of the estimates received and returns this value to the estimator together with his or her own estimate. Optionally, the estimator can submit a revised estimate to the Coordinator.

The reconciliation meeting is held and starts with each estimator being made aware of the latest median value. The purpose of this meeting is to reach a consensus regarding the estimate value. The ownership of particular estimates should remain confidential during the meeting unless someone owns up but other than using this confidentiality to avoid embarrassing particular individuals, open discussion should be encouraged. If the Coordinator feels that new estimates should be made because an important point has been agreed, for example everyone is now convinced that it is a more complex system than they originally thought, then this is perfectly acceptable.

A consensus level should be pre-specified, for example you could state that consensus has been reached when the extreme estimates are no more than thirty percent either side of the median if this was a session at the initiation stage of a fairly large project.

The value of the Delphi approach is that it involves more than one individual and it encourages discussion. It also tends to produce more accurate estimates than most organizations enjoy today.



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Software Metrics. Best Practices for Successful It Management
Software Metrics: Best Practices for Successful IT Management
ISBN: 1931332266
EAN: 2147483647
Year: 2003
Pages: 151
Authors: Paul Goodman

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