Question 1036440
<pre>
Here's what to do with a list of data.  
Start with this column of x values, add
and divide by the number of numbers to
get the mean, <span style="text-decoration: overline">x</span>.

     x 
    12 
    17 
    23 
    13
    14
    17
    20
    16 
    15
    15
  -----
10)<u>162.0</u> 
<span style="text-decoration: overline">x</span> = 16.2

Then you make another column where you subtract <span style="text-decoration: overline">x</span> = 16.2 from
each number in the x-column.
That column is labeled x-<span style="text-decoration: overline">x</span>
There is no use to add it, because if you do 
you will just get 0

     x       x-<span style="text-decoration: overline">x</span>       
    12      -4.2      
    17       0.8       
    23       6.8      
    13      -3.2      
    14      -2.2       
    17       0.8       
    20       3.8      
    16      -0.2      
    15      -1.2       
    15      -1.2       
  -----    -----           
10)162.0     0.0       
<span style="text-decoration: overline">x</span> = 16.2

We square each number in that column and
put those squares in a new column.  We
add them and divide by 1 less than the
number of numbers.           

     x       x-<span style="text-decoration: overline">x</span>      (x-x)²
----------------------------- 
    12      -4.2      17.64
    17       0.8       0.64
    23       6.8      46.24
    13      -3.2      10.24
    14      -2.2       4.84
    17       0.8       0.64
    20       3.8      14.44
    16      -0.2       0.04
    15      -1.2       1.44
    15      -1.2       1.44
  -----    -----      -----
10)162.0     0.0     9)97.60
<span style="text-decoration: overline">x</span> = 16.2            s²=10.8444...

The sample variance is 10.8444...

The sample standard deviation is the square root of
the variance, s = 3.293090409...

Edwin</pre>