STDEV (Primitive Spread Function) returns the standard deviation for a set of numbers. 
SYNTAX: 
STDEV(value1,value2,...)
REMARKS:
The standard deviation is a measure of how widely values are dispersed from the average value. 
Accepts up to 30 arguments. Each argument can be a cell, a cell range, a float value, or an integer value. 
The standard deviation is calculated using the "nonbiased" or "n–1" method. The function uses the following formula to calculate the standard deviation: 
                                                                         
The STDEV function assumes that its arguments are a sample of the population. If your data represents the entire population, then compute the standard deviation using the STDEVP function.  
EXAMPLES:
STDEV(A1,B2,C3,D4,E5,F6)
STDEV(A1:A9)
STDEV(95,89,73,87,85,76,100,96,96)=9.3422576382