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Introduction to construction statistics using Excel Chapter  1 21


             1.7.2  The mean, variance and standard deviation measures
             of central tendency

             The standard deviation is a measure of how spread out the numbers are and is
             the square root of the variance. The formula for the standard deviation is

                         h
                           	       2       2       	        2
                      S ¼   y1 Y þY2þY       þ⋯þ Yn Y =n 1Š ½
                                   "                #
                                     n
                                    X
                                s ¼    ð yi yÞ^2=n 1 ^1=2
                                    i¼1
                Excel function:
                Excel function: The standard deviation is calculated in Excel using the
                function STDEV.
                STDEV (number 1, number 2): Estimates standard deviation based on a
                sample (ignores logical values and text in the sample)


             To use the Excel statistical functions, go to quick access toolbar; select More
             Functions, and then, select Statistical.
                To produce the values, insert the formulas 5STDEV (C463-C469) and
             STDEV (C463-C469)51.95.
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