Monday, June 1, 2009

On "irrational numbers" and innumerate bloggers

Warning: Extreme nerd-dom ahead.

So there's a post at the Atlantic about the government's ownership of 60% of GM, taking on the ludicrous claim that the government now owns a large swath of corporate America. As the post correctly points out, the actual ownership of private companies by the federal government is substantially under 1/10 of 1%, which is hardly a socialist paradise. However, the reporter completely blows it with this discussion of the (admittedly rather fun) pie chart produced by Excel:

What I do see is that Microsoft Excel feels the need to portray the percentage of American companies owned by the government as an irrational number. That's 5.07e^-02, or %0.0507 of American companies that are owned by the United States. (When I ask Excel to display this breakdown in real numbers it just becomes "100%" and "0%.")
Um, no. Wrong. That's not an irrational number. It's scientific notation. An irrational number is a number that can't be expressed as a ratio of two whole numbers. It has nothing to do with whether it's written in a mantissa-exponent form (as in 5.07 * 10^-2). Scientific notation is handy for dealing with very large or very small numbers, and yes, Excel would round it to 0%, unless you asked Excel to display things out to some fixed number of decimal places.

Which is simple to do, as is suppressing scientific notation in the first place. Either one takes about 4 clicks of the mouse.

Really, people who do business reporting should be familiar with the basic functions of spreadsheet software, and if you're going to complain about something being a particular type of number, you should have some idea what you're talking about.

Update: After numerous comments in the comments section, it's been fixed so that instead of "irrational number" it says "exponential notation." All is well.


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Anonymous said...

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