Two standard deviations

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Two standard deviations
Message posted by S. Bush (via 66.88.73.50) on December 17, 2001 at 4:20 PM (ET)

I reviewed and used the explanation on how to do Standard Deviation. If I come up with 65 as my Standard Deviation how do I figure out two standard deviations? Would I multiply 65 by 2? I disposed of my Stats book many years ago. Thanks!

READERS RESPOND:
(In chronological order. Most recent at the bottom.)

Re: Two standard deviations
Message posted by Darius (via 200.23.217.10) on December 17, 2001 at 5:57 PM (ET)

There are diferent estimates of sd, each application has it愀 own and 2 sd is a strange factor (most common 3 ds).

For example: Control Charting must use an estimate of standard deviation that take in account the within sample variation and not the total variation (given by excel).

But if that what you want, it's OK to multiply 2* sd.

Re: Two standard deviations
Message posted by JG (via 128.8.23.67) on December 20, 2001 at 2:03 AM (ET)

two standard deviations is 2*sd, but the significance of sd, 2sd, etc. only has meaning if we assume normally distributed error or some other equivalent assumption

Re: Two standard deviations
Message posted by S Bush (via 66.88.73.50) on December 20, 2001 at 2:24 PM (ET)

Thank you to those who were kind enough to respond! Happy Holidays!

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