What is statistical process control in software development process?

Let us firstly see what is a defect?

A defect is an undesirable state. There are two types of defects: process and procedure. For example, if a Test Plan Standard is not followed, it would be a process defect. However, if the Test Plan did not contain a Statement of Usability as specified in the Requirements documentation it would be a product defect.

The term quality is used to define a desirable state. A defect is defined as the lack of that desirable state. In order to fully understand what a defect is we must understand quality.

What do we mean by Software Process Defects?

Ideally, the software development process should produce the same results each time the process is executed. For example, if we follow a process that produced one function-point-of-logic in 100 person hours, we would expect that the next time we followed that process, we would again produce one function-point-of-logic in 100 hours. However, if we follow the process the second time and it took 110 hours to produce one function-point-of-logic, we would state that there is “variability” in the software development process. Variability is the “enemy” of quality – the concepts behind maturing a software development process is to reduce variability.

The concept of measuring and reducing variability is commonly called statistical process control (SPC).

To understand SPC we need to first understand the following:

1) What constitutes an in control process

2) What constitutes an out of control process

3) What are some of the steps necessary to reduce variability within a process

Testers need to understand process variability, because the more variance in the process the greater the need for software testing. Following is a brief tutorial on processes and process variability.

Tags: Software Testing, Software Quality, Statistical Process Control, Quality Assurance, SPC