Paper 4 · statistics - stem and leaf

A sweet with mass greater than 1.2 g is classified as large. From the 24 masses (g) 0.72, 0.73, 0.79, 0.80, 0.88, 0.91, 0.91, 0.94, 0.98, 0.99, 1.01, 1.03, 1.06, 1.08, 1.13, 1.13, 1.13, 1.19, 1.21, 1.22, 1.33, 1.39, 1.44, 1.45, calculate the mean mass of the large sweets.

1.37

1.32

0.34

1.34

Explanation: The large sweets (mass

>1.2

g) are 1.21, 1.22, 1.33, 1.39, 1.44 and 1.45 g, six values summing to 8.04 g, giving a mean of

8.04/6=1.34

g. Excluding the borderline value 1.21 g and dividing by only 5 values gives

6.83/5=1.37

g. Wrongly including 1.19 g (which is not above 1.2 g) and dividing by 7 gives

9.23/7\approx1.32

g. Dividing the correct sum of 8.04 g by the full sample size of 24 instead of the 6 large sweets gives

8.04/24\approx0.34

Derived from ZIMSEC Maths Paper 1, June 2008, Q2 (Statistics)

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