JEE Math Practice Question
A data consists of n observations : x1, x2, . . . . . . ., xn. If $$\sum\limits_{i = 1}^n {{{\left( {{x_i} + 1} \right)}^2}} = 9n$$ and $$\sum\limits_{i = 1}^n {{{\left( {{x_i} - 1} \right)}^2}} = 5n,$$ then the standard deviation of this data is :
- A.2
- B.$$\sqrt 5 $$
- C.5
- D.$$\sqrt 7 $$
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