I know I'm gonna look so stupid to u brainy maths whizzes but I'm having some probs with standard deviation. I know how to caculate it by hand and by calculator but I'm just confused.:eek:

by hand it says minus the mean from each value and add it up, I presume that is happening in the calculator and I thought n-1 value was the just 1 of the values that ur finding the standard deviation of. but I think that bit is wrong, I don't know what to do the standard deviation of. I have Ct values from graphs that represent the expression of genes, so I don't know whether I need to do the standard deviation of each sample compared to others of the same gene or the whole lot.

Please help a poor love who is in uni but manages to scrape by without a Maths A level.:(

I'm prob making far too much out of this but please help me soon, gotta give in report on Mon.

The expression of different genes in different conditions?

You can either examine the all genes in one condition or one gene across different conditions.

Perhaps it will be clearer to you if you just try and think about what the s.d. means. You're examining variance of a particular factor in a sample (usually just a sample in bio) of something.

Apologies if I don't understand your problem.

you have to take the average of your first sample (No) and subtract from each individual, add them all and square. i.e.

(No-N1)^2 + (No-N2)^2. .. . . and so on
then I assume you have the rest of the equasion