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- 2011-7-11
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2#
发表于 2011-7-11 15:12
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gazhoo Wrote:
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> When do you use the following:
>
> 1) Point estimate (+/-) Reliability factor X
> Standard of error
>
the general formula to use when you're asked to estimate an interval within which the true mean of the population lies.
> 2) X (+/-) X(alpha/2) X (standard deviation/square
> root of n)
>
You probably mean:
X (+/-) Z(alpha/2) X (standard deviation/square root of n)
same thing, but here it is the specific formula to use when you know the TRUE population stddev
ie.
X (or more correctly, X upper dash to indicate mean value) is just the symbol for point estimate
Z(alpha/2) is the reliability factor.
- Alpha (e.g., 5%, 1%) is the probability of being in the right and left tail.
- z is normal distribution.
If you don't know the true population mean, you use the stddev of the sample which is the symbol s.
> I think it has to do with the amount of
> information that is given...can someone pls
> confirm? |
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