If you read a lot but aren’t much into math you’ve probably heard the term standard deviation being tossed around, but didn’t know what it meant exactly.

A standard deviation is a way to describe where someone (or something) falls on a scale, and, more specifically, how wide the range actually is. Bell curves are often presented when talking about standard deviations, as they capture the same idea visually.

The real question is, how far is a given measurement from the average for a group?

Some distributions are very high curves with little variation within the population, while others are short and wide.

For example, the average height for adult men in the United States is about 70 inches (178 cm), with a standard deviation of around 3 in (8 cm). This means that most men (about 68 percent, assuming a normal distribution) have a height within 3 in (8 cm) of the mean (67–73 in/170–185 cm), one standard deviation, whereas almost all men (about 95%) have a height within 6 in (15 cm) of the mean (64–76 in/163–193 cm), 2 standard deviations. Three standard deviations account for 99.7% of the sample population being studied, assuming the distribution is normal (bell-shaped).

Notes

¹ [ Standard Deviation | Wikipedia ]

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In a word–Sumerians.

First off, happy pi day.

According to a physicist at the Exploratorium in San Francisco, the number Pi has been calculated out to over one trillion digits. But that’s not the interesting part.

As it turns out, it’s totally overkill to get that precise with it. Dividing 22 by 7 gives an estimate that works for most everyday needs, such as carpentry and construction (it’s roughly 99% accurate). And calculating pi out to only 39 places gives truly astronomical precision.

Using pi calculated out to only 39 decimal places would allow one to compute the circumference of the entire universe to the accuracy of less than the diameter of a hydrogen atom.

Holy crap. So, yeah…I guess 39 places will be “good enough” then…

Oh, and just for a bit of trivia, Albert Einstein’s birthday is today, and he was a big fan of pi. But that’s not it. His birthday, like pi day, also falls on March 14th — otherwise known as 3.14. Einstein’s birthday on 3.14. Coincidence? I don’t think so. We all know God doesn’t play dice.:

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[ Thanks to NPR's Science Friday for the excellent show today! ]

I warn you. Don’t start the movie unless you have time to finish it.

[ Turning a Sphere Inside Out ]

I’ve added a new piece to the /study site. It’s a very short explanation of the birthday paradox and attack.

[ The Birthday Attack ]

e^iπ = –1

(Euler’s Equation)

I disagree, though, and find that Maxwell’s are more compelling. Less simple, sure, but more tangible and more clearly evidence of God.