Adu's scores in five subjects in an examination are 85, 84, 83, 86 and 87.
FURTHER MATHEMATICS
WAEC 2023
Adu's scores in five subjects in an examination are 85, 84, 83, 86 and 87. Calculate the standard deviation.
- A. 2.0
- B. 1.4
- C. 1.8
- D. 1.6
Correct Answer: B. 1.4
Explanation
n = 5
x? = \(\frac{∑x}{n} = \frac{85 + 84 + 83 + 86 + 87}{5} = \frac{425}{5} = 85\)
| \(x\) | \(x - x?\) | \((x - x?)^2\) |
| 85 | 0 | 0 |
| 84 | -1 | 1 |
| 83 | -2 | 4 |
| 86 | 1 | 1 |
| 87 | 2 | 4 |
| \(\Sigma(x - x?)^2 = 10\) |
\(S.D = √\frac{∑(x - x? )}{n} = √\frac{10}{5}\)
∴ S.D = √2 =1.4
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