The mean is 250.875.
Using this information, I can put the following into a calculator:
√(((250.875-195)²+(250.875-358)²+(250.875-201)²+(250.875-276)²+
(250.875-161)²+(250.875-301)²+(250.875-387)²+(250.875-128)²)÷8)
Which equals:
87.9878
This is the standard deviation of the MP3 players.
