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Fractional Factorials — WTF???

Posted by Scott Holstad on April 6, 2012

I’ve never felt so stupid as I have today. I’ve never read something and been unable to comprehend it … until now. I was reading Homer when I was 6. I read the Iliad 3 times before age 10! I’ve read books on electrical engineering, broadband networking, network engineering, existential philosophies, etc., etc. No problems. Well, I’ve been doing some transcription/editing contract work. I’ve spent the past two days working on a 6,000 word lecture on something called “fractional factorials.” I know nothing. This entire lecture, given by a native English speaker who has never heard of articles, subject/verb agreement, singular vs plural, etc., is so theoretical, there hasn’t been one concrete thing I can pick out in order to understand what the fuck he’s talking about!!! I finally found out via Google that it’s reliability engineering. I hadn’t known if it was engineering, math, or science, for God’s sake! Look at the beginning of the Wikipedia article on it:


Fractional designs are expressed using the notation lk − p, where l is the number of levels of each factor investigated, k is the number of factors investigated, and p describes the size of the fraction of the full factorial used. Formally, p is the number of generators, assignments as to which effects or interactions are confounded, i.e., cannot be estimated independently of each other (see below). A design with p such generators is a 1/(lp) fraction of the full factorial design.

For example, a 25 − 2 design is 1/4 of a two level, five factor factorial design. Rather than the 32 runs that would be required for the full 25 factorial experiment, this experiment requires only eight runs.

In practice, one rarely encounters l > 2 levels in fractional factorial designs, since response surface methodology is a much more experimentally efficient way to determine the relationship between the experimental response and factors at multiple levels. In addition, the methodology to generate such designs for more than two levels is much more cumbersome.


SHIT!!! It’s utter gibberish. I’ve had 8 hours of this shit. My brain’s about to explode. I hope I never see anything on fractional factorials again!

One Response to “Fractional Factorials — WTF???”

  1. southernhon said

    Glad that one’s done. Oh, and you just probably just expanded your brainpower by a million.


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