sum of stdev

[#1]

I have the following dataset

letter number

A        5
A        1
A        2
A        3
A        4

B        1

B         1

B         4

When I try to figure out the stdev of the dataset I have the following formula stdev(number) with dimension letter. But I am having diffculty figuring out formula for stdev divided by sum of stdev. So in A's case it would be 1.581139/(1.581139+1.732051) = 47.72% and B s case it would be 1.732051/(1.581139+1.732051) = 52.27%. I tried sum([stdev of number]) and it give me 0. Please let me know if there is a way to solve this issue.

Pivot table,  stdev of number,   % of sum of stdev

A                       1.581139                   47.72%

B                        1.732051                  52.27%

[hic]

I am not sure why you would want to sum the two numbers. Statistically it makes no sense.

But if you really want to sum the two StDev:s, then you should do a

     Sum(Aggr(StDev(Number),Letter))

HIC