I recently finished a course on Design of Experiments. It was really fascinating stuff, and very applicable to manufacturing issues. In fact, the "final exam" consisted of a group of us picking a topic and building up an experiment - this design will now be implemented in the next couple of weeks where I work. I wholeheartedly recommend reading up on this subject, or taking a class (esp. if the employer pays for it).
The question I now have is, how applicable is this to test engineering? Is it the responsibility of the test engineer to get involved in DOEs? Should test engineers consider learning how to use stat software like Minitab or JMP (both of which have extensive DOE support)?
I think it really depends on where you work. For example, if part of your job as a test engineer is dealing with SPC charts and processing test data, then DOE is a logical extension of that work. Or if you have a test system with multiple settings which need to be optimized, then DOE would be helpful. However, if you spend most of your day writing code for test systems, then it's probably just a "nice to know" thing.
BTW, the course instructor said that if you read any single book on the subject, it should be Understanding Industrial Designed Experiments by R. Launsby and S. Schmidt. It is, of course, at Amazon.com.