We just started slandered deviation in our precalcules class. We did not learn summation about sequence and series stuff. Our teacher just skipped all of that staff. I know that the standered deviation helps you to determine if the possible out comes are reasonable. How could you find the standered deviation and mean deviation? And how do you graph this I looked at the graph and it looks like a bell. In order to graph do you need to know the x and they values? I don't get what the teacher is talking about at all the formula with the sigma sign it doesn't make any sence to me. I don't have any resources that I could learn these things. Our teacher has all ready collected our books. IF you if you give me some sites that might be help full to me that would be really great.