First, sum the data: 498, then divide by the number of data=498/11=45.27 approx. This is the mean.
Next, we need to subtract the mean from each of the data and square it:
-124/11 127.0744
228/11 429.6198
-36/11 10.7107
250/11 516.5289
-168/11 233.2562
-36/11 10.7107
-25/11 5.1653
-102/11 85.9835
195/11 314.2562
-91/11 68.4380
-91/11 68.4380
Now we add up the squares: 1870.1818 and divide by 11=170.0165. This is the variance and the SD is the square root=13.04.