Returns for the Dayton Company Over the Last 3 Years

Multiple Choice

Returns for the Dayton Company over the last 3 years are shown below.What's the standard deviation of the firm's returns? (Hint: This is a sample, not a complete population, so the sample standard deviation formula should be used.)
Year Return 2011 21% 2010 -12.50% 2009 25%

A) 20.08%
B) 20.59%
C) 21.11%
D) 21.64%
E) 22.18%