Stuart McLachlan
stuart at lexacorp.com.pg
Tue Jan 18 16:14:04 CST 2005
On 18 Jan 2005 at 16:03, pedro at plex.nl wrote:
> But now. You gave me an example of the calculation {So if the points are
> 8.4 and 9.3, the average is 8.85. The "standard deviation" would be 9.3
> - 8.85 = 0.45.}. Steve your calculation is the stdevp. This calculation
> is for a whole population. But, i understand, that it doesn't matter.
> The calculation can't be done in access because it needs a field name.
> It it possible to write the two values each time to a temp field, do the
> calculations and write them then to the result table.
>
SD of a population uses Sqr(..../N), SD of a sample uses Sqr(...../(N-1))
Since there are only two data points (N=2), the difference between StdDevP
and StdDevS is SQR(..../2) v SQR(......) Since Sqr(2) = 1.414, you end
up with StDevS = StdDevP *1.414 or
StDevS = Abs(A1-B1)/2*1.414 = Abs(A1-B1)*0.707
--
Stuart