Adu’s scores in five subjects in an examination are 85, 84, 83, 86 and 87. Calculate the standard deviation.
- 2.0
-
1.4
- 1.8
- 1.6
The correct answer is: B
Explanation
n = 5
x̄ = \(\frac{∑x}{n} = \frac{85 + 84 + 83 + 86 + 87}{5} = \frac{425}{5} = 85\)
| \(x\) | \(x - x̄\) | \((x - x̄)^2\) |
| 85 | 0 | 0 |
| 84 | -1 | 1 |
| 83 | -2 | 4 |
| 86 | 1 | 1 |
| 87 | 2 | 4 |
| \(\Sigma(x - x̄)^2 = 10\) |
\(S.D = √\frac{∑(x - x̄ )}{n} = √\frac{10}{5}\)
∴ S.D = √2 =1.4