I don't know but this website would help
http://www.mathsrevision.net/gcse-maths-revision/statistics-handling-data/standard-deviation
type in this link http://www.mathsisfun.com/data/standard-deviation.html
it will help
I don't know but this website would help
http://www.mathsrevision.net/gcse-maths-revision/statistics-handling-data/standard-deviation