Fn key. Not to be confused with Function key. The Fn key, short form for function, is a modifier key on many keyboards, especially on laptops, used in a compact layout to combine keys which are usually kept separate. It is typically found on laptops due to their keyboard size restrictions.
For a finite set of numbers, the standard deviation is found by taking the square root of the average of the squared deviations of the values from their average value. For example, the marks of a class of eight students (that is, a population) are the following eight values:
Standard deviation: It is the square root of mean/average of squared deviations of data point from mean i.e. we subtract the mean from each data point; take it's square value (which is again non-negative); sum it up and divide by the number of observations. Surely, standard deviation is a better & most commonly used measure of variation.