How do you fins the standard deviation (SD) for a set of numbers?

I have this on a test next week and don't understand how to get it. I've looked it up online but I need someone to put it in laymens term for me.





Thanks!How do you fins the standard deviation (SD) for a set of numbers?
1. Find the mean (average) of the set of numbers. (6+7+2=15; divided by 3= 5)


2. Find the deviation of the individual numbers from the mean. (15-6=9, 15-7=8, 15-2=13 )


3. Square each of the deviations.( 9x9=81, 8x8=64, 13x13=169)


4. Add the squares. (81+64+169=314)


5. Divide by total number of numbers in answer less one (314 divided by 2=157)


6. Take the square root of this result to get the Standard Deviation


(square root of 157 = 12.529964) This is your standard deviation.





To summarize:





1) Average the set of numbers.


2) Subtract each original number from the average to get deviations


3) Multiply each deviation by itself to square


4) Add the squares


5) Divide this result to the total number of numbers in the original set, minus 1 ( if 7 total numbers in set, divide by 6)


6) Square this resultHow do you fins the standard deviation (SD) for a set of numbers?
as far as I know ))





s=(sigma xi - xaverage)^2/ (n-1)





first you find xaverage of set of numbers, then you subtract it from each number from the set, then square it and find the sum of all squares





your table should look like





n.........xi...........xi-x.aver. ........(xi- x.aver.)





where n is number of data


xi is each data from the set


xi-x.aver.- subtract x.aver. from each data point


and (xi-x.aver.)^2 - square it





sigma is sum of all squared results





hope it helps ))

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