i wonder how many people understand standard deviation? probably less than 50% of the general public.
. . .Give or take 49%.
Actually, I don't completely understand it. I know that something like 2/3 of the population is within one standard deviation of the mean, 85% for 2 standard deviations, and 95% for 3 standard deviations. (And even those numbers, I'm pulling out of my head without a lot of confidence.)
And I only have a vague idea of how it's calculated. I have a researcher friend who does statistical analysis as part of his job--and he uses terms I don't understand--but I doubt anyone else I know has much reason to ever calculate a standard deviation.