GRE
The standard deviation of the seven numbers $$-c, -b, -a, 0, a, b, c$$
The standard deviation of the seven numbers $$-c^{2}, -b^{2}, -a^{2}, 0, a^{2}, b^{2}, c^{2}$$
The standard deviation of data set Ⅰ
The standard deviation of data set Ⅱ
The area of region $$S_1$$ minus the area of region $$S_3$$
$$\frac{π}{2}-1$$
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