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Comment of the Fortnight
18 August 1998
It's Not Easy Being Stupid

So a friend called me last night and asked me if I could do a web page or spreadsheet that does calculation of bodyfat percentages based on skin fold measurements. "Sure," I said. "Just fax me the formulas."

He sent me a rather blurry fax which contained the following equations:

Lohman Equation:
    DENSITY = 1.0973 . (SUM x .000815) + (SUM)2 x .00000084
(where SUM is the sum of the skinfold measurements)

Brozek Equation:
    BODYFAT = (4.57 / DENSITY - 4.142) x 100

I took the symbol after the "1.0973" in the first equation to be the raised dot used to symbolize multiplication. I started writing a form and the Javascript to do the calculations, and came up with bodyfat percentages of 16152.7% with a one centimeter skin fold. Clearly, something was very wrong here.

Most of you are probably saying, "This guy really is stupid. The problem is obvious." Well, it wasn't to me. In a fit of stupidity, I went on a web search to find out if the equations were correct or not. I found the Brozek equation almost immediately -- it was correct. I couldn't find the Lohman Equation after forty-five minutes of searching.

It was 12:47 in the morning, so I gave up. Just as I turned the computer off, I realized how incredibly stupid I was.

  1. Why would they use both the raised dot and x symbol for multiplication in the formula?
  2. If the sum of the skinfolds turns out to be zero, the Lohman equation would result in a body density of zero, which is clearly impossible.
Click. The light bulb came on.
You idiot. That's not a raised dot. It's a minus sign that got blurred in the fax.
I took a calculator and ran a couple of examples using subtraction instead of multiplication. Sure enough, I got reasonable results.

So, what I want to know is: how come I never figure these things out until after I've wasted the better part of an hour chasing down blind alleys? Why is it always after I've turned off the computer? It's not easy being stupid.

In Other News...

I watched the media circus that went on after President Clinton's speech about his testimony to the grand jury on 17 August 1998. Two things I noticed:

  1. James Traficant, Democrat from Ohio, must have gotten hair styling advice from Don King.
  2. I was amused to see Bob Barr, Republican from Georgia, speaking about morality. This is the guy who wrote the "Defense of Marriage Act," and is in the process of defending his third marriage. I don't believe either of the first two wives has died yet, so I guess "till death do us part" isn't included in marriage ceremonies in Georgia. Otherwise, he wouldn't be following his marriage vows terribly well, would he?

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