Delphi Cost Estimation Model In Software Engineering

Delphi Cost Estimation Model In Software Engineering

Delphi cost Estimation predicts the requirement of money and resources which is to be used for the software development process.

Software cost and the efforts estimation for software development process is never will be an exact science.
There are too many variables like human efforts, technical efforts, environmental efforts can affect the estimated cost of the software and efforts applied to develop it.

Delphi technology is quite old but efficient forecast method. It follows an interactive approach that depends on the exchange of ideas. The team is composed of a group of experts in their respective domains, which answers the questions in two or more rounds. Each time a facilitator provides a summary of the collected ideas, which is modified by experts, if necessary. The process of feedback and re-evaluation continues until the last consensus is formed.

Delphi technology relies on its assumption on the fact that it is a productive result by assimilating ideas from a structured group

Delphi Cost Estimation Model Slide

  • Delphi Cost Estimation Model in Software Engineering

  • Delphi Cost Estimation Technique

In Delphi Cost Estimation-Model

To keep the trust of the stakeholders (customer) on the project manager or the team the estimation of the project should be realistic at the beginning.

Unless you are not sure about your estimation that your estimation is accurate, you will not be able to make much progress in a software project

Now, let us discuss Delphi Cost Estimation-Model In Software Engineering more briefly by using some pictures and slides. So, let’s start:-

Delphi Cost Estimation Model in software engineering is a structured communication technique, which is originally developed as a systematic and interactive forecasting method which relies on a panel of project developers(experts). They answer questionnaires in two or more rounds. After each round, a facilitator provides an anonymous summary of the experts’ forecasts from the previous round with the reasons for their judgments. The panel of Experts is then encouraged to revise their earlier answers in light of the replies of other members of the panel.

During this process, the range of answers will decrease and the group will converge towards the “correct” answer.


Delphi Cost Estimation Model in software engineering was developed in the 1950-1960s at the RAND Corporation.

Wideband Delphi Technique in Software Engineering

Wideband Variant of the Delphi Method was originated by Barry Boehm and John A.Farquhar in the 1970s. The word “Wideband” is used because as compared to the Delphi Method, the wideband Delphi technique involved greater interaction and more communication between the user or participants.

In this technique, the estimation team comprises the project manager, moderator, panel of experts, and representatives from the development team, constituting a 3-7 member team.

In Delphi Wideband Technique there are two types of Meetings. They are:-

  • Kickoff Meeting
  • Estimation Meeting

Wideband Delphi Technique is a consensus-based assessment technique to assess the technique effort.

Wideband Delphi Method has proved that it is a very effective cost estimation tool, and lends itself well to software projects.

We discussed about Wideband Delphi. So, now let us discuss the steps which should be followed to estimate the cost of the project.

Steps for Wideband Delphi Model

  • In the first step, we have to select the Estimation Team and a moderator.
  • The second step the moderator conducts the kickoff meeting, In that meeting, the team will be present with the problem specification and a task list. If any problem and estimation issue will be there the team panel will discuss the problems. The team will also decide on the units of estimation. The moderator guides the whole discussions and monitors time and after the kickoff meeting, prepares a structured document which contains problem specification, high-level task list, assumptions, and the units of estimation that are decided in the meeting. Then the moderator forwards copies of the documents for the next steps.
  • Now in the third step the each and every team member of Estimation team individually creates a complete detailed WBS ( work breakdown structure ), they estimate each task in WBS, and documents the assumptions are made.

Wideband Delphi Estimation Sheet1

Wideband Delphi Estimation Sheet1
Delphi Cost Estimation-Model In Software Engineering
  • Now, In Step number 4 The moderator calls the Estimation team for the Estimation meeting. If anyone of the members of the estimating team will say that the estimates are not completed or not ready then the moderator have to give more time to the team members.
  • The entire estimate team estimates gather for the meeting. At the beginning of the estimation meeting, the moderator collects preliminary estimates from each team member. He then puts a chart on the whiteboard. He presents each member’s total project estimate in the form of X on the round 1 line, without revealing related names. The estimation team gets an idea of the extent of estimates, which can be initially larger.
  • Now Each team member reads the detailed work list which he/she has created, identifying any assumptions and raising any questions or issues. Work estimates are not disclosed. Individual detailed work lists contribute to the more complete list of events. After this, The team then discusses any doubts/problems that are about the issues, assumptions, and estimation of the issues they have.
  • The members of each team revisit their work list and assumptions and make changes if necessary. Work estimates may also require adjustments depending on the discussion, which is known as + N Hrs. For more effort and at -NH For less effort. Team members then add a change in the work projections to reach the total project estimate.

Wideband Delphi Estimation Sheet2

Wideband Delphi Estimation Sheet2
  • Now in Step 6 The moderator collects the changed estimates Moderator collects estimates that have changed from all members of the team and plots them on the round 2 line. In this round, the range will be narrower than before, because it is based on more consensus.
  • The team then discusses the work amendments and assumptions made.
  • The members of each team revisit their work list and assumptions and make changes if necessary. Work estimates may need adjustments based on the discussion. Team members add changes to work estimates once again to reach the total project estimate.
  • The moderator again collects converting estimates from all the members and plots them on the round 3 lines.
  • Again, in this round, the range will be narrow compared to the first.
Delphi Cost Estimation Model
  • Now in the last step, The Project Manager then collects results from Estimate Meeting. He compiles individual work listings and related estimates in the same master job.
  • It also adds personal lists of assumptions. Then he reviews the final work list with the estimation team.

These are the steps which are followed in the Delphi Cost Estimation Model in software engineering.

Now let us talk about the advantages and disadvantages of Delphi Cost Estimation Model in software engineering.

Advantages of Delphi Technique

  1. Delphi Cost Estimation Model is a consensus-based assessment technique to assess the technique effort.
  2. The Delphi Technique is useful when evaluating time to do a task.
  3. The participation of experienced people and they will get reliable results by estimating personally.
  4. Those people who work will be guessing and thus making a valid guess.
  5. To maintain anonymity makes it possible for everyone to express their results with confidence.
  6. Delphi Method is a very simple technique.
  7. Beliefs(assumptions) are documented, discussed and agreed.
  8. Implementation is easy and cheap.
  9. The Delphi Estimation Model is used for high level and detailed estimates.
  10. Wideband Delphi Method gives more accurate results than LOC(Lines of code) and FP(Function Point)
  11. While conducting the estimation process, most participants are friendly to the aspects of the project.

Disadvantages Of Delphi Technique

  1. Management support is necessary.
  2. Estimation cannot be the result of what the management wants to hear.
  3. In the Delphi technique no guidelines for determining consensus, sample size, and sampling techniques.
  4. Time/participant commitment is required.
  5. The delay between visits in the data collection process (many data collection, analysis, processing)
  6. Difficult to repeat with a different group of experts repeatedly.
  7. You can probably reach a consensus on the wrong assumption.
  8. The wrong feeling of confidence develops many times.
  9. Experts can be biased in the same direction of purpose.
  10. Experts may fail to reach consensus or refuse to reach consensus.
  11. Drop-out, response rates (relying on a quick response by busy experts).

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