what does it mean deviation in statistics?

Answer 1

it's actually tied to the variance, which is easier to calculate (the standard deviation is the square root of the variance). It's hard to tell you how to calculate these in general, but for a sample you can calculate the mean by summing up the values and dividing by the number of them (i.e. if you have a sample of size n, take the sum of all n values and then divide by n). This is the mean and then the sample variance is found the following way:

If x_{j} is the jth element and y is the mean, then take the sum (from j=1 up to j=n) of (x_{j}-y)^{2} and then divide by n-1 (NOT n!). The standard deviation will then just be the square root.

I hope this helps. I realize this is a tad difficult to understand, but it's really not an easy question to answer.

Answer 2

it is the average number that can vary from the mean....
it is determined bysubtracting the mean from each of the n samples.
if the values are small then there is little varience from the mean.