calculating standard deviation

[Bob Weiner]

How do I calculate the standard deviation when given intervals and number of
occurances. For instance:

Interval Occurances
10 2
20 0
30 0
40 2

What I need is stdev (10, 10, 40, 40)

It would seem there would be an obvious way to calculate this but google
couldn't find any examples.

thanks,
bob

 

[Bob Weiner]

Never mind, I figured it out. (I did try before posting, really)