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

Mathematics

JAMB 1992

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. \(\sqrt{\frac{3}{2}}\)

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Correct Answer: Option C

Explanation

(x) = \(\frac{5 + 6 + 7}{3}\)

= \(\frac{18}{3}\)

= 6

\(\begin{array}{c|c} scores(X) & \text{d = (x - x) deviation} & (deviation)^2\\\hline 5 & 5 - 6 & 1\\ 6 & 6 - 6 & 0 \\ 7 & 7 - 6 & 1\\ \hline & & 2\end{array}\)

S.D \(\sqrt{\frac{\sum d^2}{n}}\) where d = deviation = (x - x)

= \(\sqrt{\frac{2}{3}}\)

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