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If the scores of 3 students in a test are 5, 6 and 7, find…

If the scores of 3 students in a test are 5, 6 and 7, find the standard deviation of their scores
  • A.
    (frac{2}{3})
  • B.
    (frac{2}{3}sqrt{3})
  • C.
    (sqrt{frac{2}{3}})
  • D.
    (sqrt{frac{3}{2}})
Correct Answer: Option C
Explanation

(x) = (frac{5 + 6 + 7}{3})
= (frac{18}{3})
= 6
(begin{array}{c|c} scores(X) & text{d = (x – x) deviation} & (deviation)^2\hline 5 & 5 – 6 & 1\ 6 & 6 – 6 & 0 \ 7 & 7 – 6 & 1\ hline & & 2end{array})
S.D (sqrt{frac{sum d^2}{n}}) where d = deviation = (x – x)
= (sqrt{frac{2}{3}})

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