### 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.

- Why would they use both the raised dot and
`x` symbol for multiplication
in the formula?
- 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:
__

- James Traficant, Democrat from Ohio, must have gotten hair styling advice
from Don King.
- 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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