MCQ
The standard deviation of the data $6, 5, 9, 13, 12, 8, 10$ is:
  • $\sqrt{\frac{52}{7}}$
  • B
    $\frac{52}{7}$
  • C
    $\sqrt{6}$
  • D
    $6$

Answer

Correct option: A.
$\sqrt{\frac{52}{7}}$
$\sqrt{\frac{52}{7}}$
Given data are $6, 5, 9, 13, 12, 8$ and $10$
$x_i$ $x_i^2$
$6$ $36$
$5$ $25$
$9$ $81$
$13$ $169$
$12$ $144$
$8$ $64$
$10$ $100$
$\sum\text{x}_\text{i}=63$ $\sum\text{x}_\text{i}^2=619$
$\therefore\ \text{SD}=\sigma=\sqrt{\frac{\sum\text{x}_\text{i}^2}{\text{N}}-\Big(\frac{\sum\text{x}_\text{i}}{\text{N}}\Big)^2}$
$=\sqrt{\frac{619}{7}-\Big(\frac{63}{7}\Big)^2}=\sqrt{\frac{4333-396}{49}}$
$=\sqrt{\frac{396}{49}}=\sqrt{\frac{52}{7}}$

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