View Full Version : % within x SDs of mean question
DavidC
08-04-2005, 04:16 AM
I'm curious... how much % of the curve on a standard distro is within 1 SD of the mean?
2 SD?
3 SD?
(My guess: 67/90/95, or 67/99/99.5)
emp1346
08-04-2005, 04:25 AM
in a standard normal distribution with a mean of zero,
1 SD: .3413 or +/- 1 SD: .6426
2 SD: .4772 or +/- 2 SD: .9544
3 SD: .4987 or +/- 3 SD: .9974
As an additional note, that's why Six Sigma is so common in business applications, because it represents 99.74% of the distribution...
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