Statistics 101

The Assistant Village Idiot has up a short and sweet post on proof:

Whenever I come across the word proves in a news story or a comment section, I usually think “Here’s someone who didn’t take enough math courses.”

I feel the same way when some says “that’s statistics 101”.

Example: I was reading a story recently on a particular type of forensic testing that was coming under some question (I was a lab tech in a former life, these things interest me).  Anyway, the study author was quoted as saying that 15% of the samples they were able to test showed some contamination, with the caveat that only one third of the samples in storage were still testable and thus the percentage could be subject to change.

When I was reading the comments section, one of the commenters got quite irate that this was being presented as only a 15% potential error rate.  Since only a third of samples were tested, he claimed we should actually multiply by 3 to get the real error rate….45%.  That’s Statistics 101!

Sadly this is a blog with lots of angry and under educated commenters*, so the next 3 follow up comments were all along the lines of “nice catch”.

Math, it’s how you know when people are lying to you (but only if you do it correctly).

*This is another “not going to link to it for fear of track-back vitriol” blog citation.  But if you’re curious, it’s a blog tackling the issue of false criminal accusations.  While it’s a real and important issue, it does attract a good number of irrational people who hate the world and leave comments expressing their feelings quite….disturbingly.  The guys who run it seem pretty fair though, and I like reading the forensics aren’t perfect stuff, CSI be damned.

One thought on “Statistics 101”

1. Similarly, I like to say that you can get statistics to tell you the truth, but sometimes you have to grab them by the lapels and say “Tell me who your friends are.”

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