Six Sigma is a methodology for improving the quality of production. It was developed by the company Motorola in the early eighties, and it is successfully applied in many software development companies. The purpose of Six Sigma is to make a product of constant quality with statistically measured estimation of defects, improvement of process for eliminating defects, and monitoring these improvements. Six Sigma is successfully applied for improving the organizations in various spheres.

While it has a successful reputation in big companies with thousands of employees, Six Sigma also may be applied in small design teams. This makes it being used by many small web development teams to improve their processes. The basis of the methodology Six Sigma is made by an estimation of deviations of actual metrics of process from a curve of normal allocation of deviations. If those or other metrics of process are in certain limits of deviations, the quality of process results also remains high. In statistics it is accepted to name a unit of measure of deviations as “sigma”.

The appreciable effect is observed at deviation no more than 4,5 sigma; In this case the metric of number of defects on one million units of production makes 3,4. But this condition is fulfilled in stable processes. Productions usually aren’t stable. The inventors of methodology have come to a conclusion that the deviations of the process, called by its natural instability, give quality deviations at level 1,5 sigma.

Thus, if the target degree of quality is made by 4,5 sigma taking into account 1,5 sigma on deviations it is necessary to provide a degree of quality in 6 sigma. ”To reach such degree of quality in production, 99.9997 % from a total number of products should be of comprehensible quality (or 3.4 defects on one million possible). Deviation is the important part of Six Sigma. Here what one of the pioneers and innovators of the methodology has said: “Our clients feel Deviation, instead of the Average.” All processes have some heritable deviation. There are no software processes which generate defects with a constant coefficient. Here Six Sigma is especially effective.

The purpose of Six Sigma is to think of each aspect of business as about a process which can be improved and can be measured statistically. The main tool is the approach consisting of 5 stages named DMAIC (define, measure, analyze, improve, control).

There are a lot of words said about web development and functional programming methodologies. Usually they are oriented to development mostly and do not deal very much with testing. So should testing have a separate methodology?

It is not a secret that quality software is one of the most important requirements for a customer. It often doesn’t matter the timeframe or even the budget of the project, but whether the end users will be pleased with the product developed. So the importance of testing is great and on some projects good testing is even more valuable than good development. Anyway this doesn’t mean that testing should have a separate methodology. As testing is a very agile and flexible process, which closely connected with web application development, there should be the same methodology for testing as for development.

Testing is flexible enough to choose the best process to achieve the result easily and quickly. It can be various, depending on the development methodology, project team specification and customer’s goals.
If you think of a separate testing methodology – just take all the best practices together and work out your own testing methodology!

The iterative development model is a cyclic software development process, developed to oppose the waterfall model and its weaknesses. It is an essential part of the agile software development and often is used in web application development.

The main idea of the iterative methodology is to produce a software system incrementally, allowing the web developers to take advantage of what was being learned during the earlier software development, and produce incremental, deliverable builds of the system. Learning comes from QA, testing, programming and coding, and use of the system. The process itself looks like that: start of the web development with a simple implementation of a subset of main and the most important requirements and iteratively enhance it with additional features until the full system is implemented. At each iteration, design modifications are or may be made and new features are added.

The development process consists of the following steps: initialization, iteration, and the project control list. The initialization step creates a prototype of the system or a base version. The main goal for this initial implementation is to create a software build to which the customer can react and if necessary give the development team new requirements or enhance the existing ones.

To manage and guide the development process, a project control list is created, which contains a set of all tasks that need to be implemented. It includes new features to be implemented and areas of redesign of the existing application. As a result of the analysis phase the control list is constantly being revised to improve the functionality on next iteration.

Each iteration involves the implementation of the needed features form a control list, redesign of the needed functionality, and the analysis of the current version of the system. The goal for the implementation and design of any iteration is to be simple and modular, supporting redesign if needed. Design detail level in such model is subject to discuss and should be chosen for the project specifically, depending on the project itself. In this case the iterative model doesn’t dictate the needed level of detail.
The analysis of iteration is based upon customer’s feedbacks. Also, it involves the analysis of the interface usability, reliability, efficiency, structure, modularity and achievement of the main goals. When the analysis is over, the IT project control list may be modified, depending on the results.