MCQ
If the data $x_1, x_2, ...., x_{10}$ is such that the mean of first four of these is $11$, the mean of the remaining six is $16$ and the sum of squares of all of these is $2,000$; then the standard deviation of this data is
  • A
    $2\sqrt 2 $
  • $2$
  • C
    $4$
  • D
    $\sqrt 2 $

Answer

Correct option: B.
$2$
b
${x_1} + ... + {x_4} = 44$

${x_5} + ... + {x_{10}} = 96$

$\bar x = 14,\sum {{x_i} = 140} $

Variance $ = \frac{{\sum {x_i^2} }}{n} - {{\bar x}^2} = 4$

Standard deviation $=2$

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