Paper 2 · descriptive statistics / grouped data

In a survey of 100 athletes at a marathon, the amount of water taken, in litres, was recorded as: 0-0.5 litres by 8 athletes, 0.5-1.0 litres by 20 athletes, 1.0-1.5 litres by 29 athletes, 1.5-2.0 litres by 22 athletes, and 2.0-2.5 litres by 21 athletes. Using the midpoint of each class, what is the estimated mean amount of water taken, in litres?

A1.35

B1.45

C1.39

D1.30

Explanation: Using midpoints 0.25, 0.75, 1.25, 1.75, 2.25: mean

= \frac{8(0.25)+20(0.75)+29(1.25)+22(1.75)+21(2.25)}{100} = \frac{139}{100} = 1.39

litres.

Derived from ZIMSEC Statistics Paper 2, November 2019, Q2

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