A data consists of n observations: \({x_1},{x_2}, \ldots .,{x_{\rm{n}}}.{\rm{\;If\;}}\mathop \sum \limits_{i = 1}^{\rm{n}} {\left( {{x_i} + 1} \right)^2} = 9{\rm{n\;and\;}}\mathop \sum \limits_{i = 1}^{\rm{n}} {\left( {{x_i} - 1} \right)^2} = 5{\rm{n}}\), then the standard deviation of this data is:

A data consists of n observations: \({x_1},{x_2}, \ldots .,{x_{\rm{n}

1.	A data consists of n observations: \({x_1},{x_2}, \ldots .,{x_{\rm{n}}}.{\rm{\;If\;}}\mathop \sum \limits_{i = 1}^{\rm{n}} {\left( {{x_i} + 1} \right)^2} = 9{\rm{n\;and\;}}\mathop \sum \limits_{i = 1}^{\rm{n}} {\left( {{x_i} - 1} \right)^2} = 5{\rm{n}}\), then the standard deviation of this data is:
A.	2
B.	√5
C.	5
D.	√7
Answer» C. 5