For the frequency distribution: Variate $x: x_1, x_2, x_3, \ldots, x_{15}$
Frequency $f: f_1, f_2, f_3, \ldots, f_{15}$
where $0 < x_1 < x_2 < x_3 < \ldots < x_{15} = 10$ and $\sum_{i=1}^{15} f_i > 0$, the standard deviation cannot be