I forgot the forumla for standard deviation...

I'm writing a program to dynamically allocate some memory for an array...

Then I gotta use that to find standard deviation...

All is easy until the stupid forumla....

Can anyone give me a very simply breakdown of the formula so i can use it in my program?

Thanks in advance.

Cheers,

Bryan

 

Call your data points x1, x2, . . . , xn.

Let S = (x1^2 + x2^2 + . . . + xn^2) / n.

Let M = (x1 + x2 + . . . + xn) / n. (M is the mean.)

Variance: V = S - M^2.

Std. Dev. = sqrt(V).

Example:

Data: 1, 2, 3, 4, 5

S = (1 + 4 + 9 + 16 + 25) / 5 = 55 / 5 = 11.

M = (1 + 2 + 3 + 4 + 5) / 5 = 3.

V = 11 - 9 = 2

SD = 1.414...

 

Thanks magician...

You sure are full of magic...

(sorry for the cheesy line)

Cheers,

Bryan