how do you find the standard deviation of something?

Question

Please give a mathematical example. Thanks.

Answer 1

http://www.easycalculation.com/statistics/learn-standard-deviation.php

Answer 2

standard deviation means how far the "typical" data point is expected to fall from the mean

you will need a list of data (data points)

first you find the mean (average)
then you find how far each data point varies from that mean(just subtract)
then you square that deviation
do the same for each data point
sum all the squares
divide by how many data points (to find the avg deviation)
take the square root of that sum

So, data = 5, 7, 9

mean is 7
5 devates by 2, and 9 deviates by 2, and 7 deviates by 0
square of 2 = 4, square of 2 = 4, square of 0 = 0
total of the squares = 8
divide that total deviation by 3 = 2.6667
square root of that = 1.63

standard deviation is 1.63

how's that?

Answer 3

You don't find the standard deviation of "something" - you find standard deviation of a list of values. Explanations and examples can be found at the link below.

Answer 4

http://www.easycalculation.com/statistics/learn-standard-deviation.php

has an example.