std does not give good values?

Hello everybody,

For this matrix

M = [1 2; 3 4];

if we compute the its standard deviation

std(M(:))

then we obtain 1.2910, while by definition, it should be 1.1180. Why is there such a difference?

Thank you for your help.

Answer 1

[Roger Stafford]

The 1.2910 value is the unbiased standard deviation which is default while the 1.1118 value is the second moment. Read the documentation for 'std' at:

 http://www.mathworks.com/help/matlab/ref/std.html

[f10w]

Thanks, Roger.