Normalization and Standard derivation - (Jun/12/2006 )

Hi there!

I need some help with my calculations if possible. I just don't know how to calculate the standard derivation...The problem is this:

I have a lot of samples but I will explain it with 12 samples, always 3 of them are triplicates...lets say A1 A2 A3, B1 B2 B3, C1 C2 C3, D1 D2 D3.

In addition to that I have 3 samples for Background correction, E1 E2 E3.

What i have done is: mean value of the Triplicates so A, B, C, D, E as mean values, corrected all thge values with substraction of the background and then i calculated the ratio of B/A and D/C and performed Normalisation with (1) B/A divided by B/A and (2) D/C divided by B/A. so (1) = 1 = 100% and (2) = 0,6 =60%. Now i need to calculate the standard deviation on these normalized values...Don't know how though...

Hope anyone can help me!

Regards Stardust

Standard deviation:

http://en.wikipedia.org/wiki/Standard_deviation