Thursday, August 13, 2009

Significant Digits

Stumbling around the Internet this morning I ran across this post:
"Their findings aren’t all that favorable to those of us with lofty views of Twitter, because as it turns out, 40.55% of tweets are pointless babble."
I didn't click further to see how they defined "babble" or how they determined whether the babble was of the pointless or pointed variety. What stopped me cold was the precision of 40.55%. Not 40% or 45% or even 41%. 40.55%!

One of the concepts I learned in engineering school was that of significant digits. Way too many folks don't understand this important principle. For the innumerate it is the functional equivalent of a grammar error. It reflects poorly on the credibility of the author.

One-third of a million isn't 333,333, it's about 330,000. Any number more precise than that is drivel. There are only one or two significant digits in a million ( between 500,000 and 1,500,000 or even between 900,000 and 1,100,000) so a third of that number has only one or two significant digits.

That's today's lesson in Numeracy. For further reading, go to this book. I recommend it!

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