Re: Calculate Standard Deviation with R

R User wrote:
"Bruce Weaver" <bweaver@xxxxxxxxxxxx> a écrit dans le message de news:

--- snip ----

Descriptive Statistics
|---------------|--|-------|-------|------|--------------|--------|
| |N |Minimum|Maximum|Mean |Std. Deviation|Variance|
|---------------|--|-------|-------|------|--------------|--------|
|x |50|496 |504 |500.06|1.823 |3.323 |
|---------------|--|-------|-------|------|--------------|--------|
|Valid N |50| | | | | |
|(listwise) | | | | | | |
|---------------|--|-------|-------|------|--------------|--------|

The SD and variance are computed with n-1 in the denominator. With division by N, the variance would be approximately 3.323 * 49/50 = 3.165.

I find the same results as you but why do you minore N by 1 : 50- 1 ?

Dividing by n-1 gives you an unbiased estimate of the population variance.

--
Bruce Weaver
bweaver@xxxxxxxxxxxx
www.angelfire.com/wv/bwhomedir
.

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