NECO 2024 · Paper 1 · Q53

Dispersion & cumulative frequency

Calculate the variance of 30, 28, 35, 25, 37.

Worked solution (try it first)

The numbers add up to 155, so the mean is 31.
The deviations are $-1$ , $-3$ , 4, $-6$ , 6.
Their squares are 1, 9, 16, 36, 36, which add up to 98.
The variance is $\frac{98}{5} = 19.6$ , option C.

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