Sunday, July 26, 2009

Intro to Statistical Process Control (SPC)

In exploring the web about Deming stuff I stumbled upon this site from Steve Horn. It introduces Statistical Process Control (SPC).
There are a number of pages on various aspects, like

The articles are read quickly and understood easily. They are written to the point.

I'd like to add that in Deming's 14 Points, Point 3 needs a special interpretation for software or (IT) project people.
The point says: 
3. Cease dependence on inspection to achieve quality. Eliminate the need for inspection on a mass basis by building quality into the product in the first place.

Deming was talking about (mass) production. In that field, "inspection" means roughly the same as "testing" in our profession.
In fact, inspections (of requirements, designs, code and test cases) are among the most effective activities you can do in software, for building quality into the product in the first place.

BTW, if you worry about your software development organisation NOT really testing their products, it is a very wise idea to first introduce a couple of  inspection stages, for this is both more efficient (economic) and effective (less defects). It is also a sensible way to introduce learning. 
Testing is about finding defects, Inspections are about pointing out systematic errors and give people a real chance for preventing them in the future.

Here's one quote from Steve I like in particular:
Confident people are often assumed to be knowledgeable. If you want to be confident the easiest way is to miss out the 'Study' phase (of the Plan-Do-Study-Act-Cycle) altogether and never question whether your ideas are really effective. This may make you confident but it will not make you right.

(words in brackets are mine)

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