Given that the mean of the scores 15, 21, 17, 26, 18 and 29 is
MATHEMATICS
WAEC 2012
Given that the mean of the scores 15, 21, 17, 26, 18 and 29 is 21, calculate the standard deviation of the scores
- A. \(\sqrt{10}\)
- B. 4
- C. 5
- D. \(\sqrt{30}\)
Correct Answer: C. 5
Explanation
\(\begin{array}{c|c} x & x - x & (x - \bar{x})^2\\ \hline 15 & -6 & 36\\21 & 0 & 0\\17 & -4 & 16\\ 26 & 5 & 25 \\ 18 & -3 &9 \\ 29 & 8 & 64 \end{array}\)
\(E(x - \bar{x})^2\) = 150
N = 6
S.D = \(\sqrt{\frac{(x - x)^2}{N}}\)
S.D = \(\sqrt{\frac{150}{6}}\) = 5
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