Sorry if this is a very basic question, my statistics knowledge is very low!
I've got a dataset which is basically a set of greyscale values in a greyscale texture (ie. 0-255). What I want to do is take the mean value, and find out what the values would be at a specified standard-deviation to the left and right of the mean. Is this possible? I presume I'd have to presume a normal distribution?
I hope that makes sense!