WAEC 2015 Mathematics · Question 31

Score 0 - 4 5 - 9 10 - 14 Frequency 2 1 2 The table shows the distribution of the scores of some students in a test. Calculate the mean scores.

Options

A.5.6
B.6.2
C.6.6
D.7.0

Answer: D. 7.0

Explanation written with AI and checked against the answer key

Analyze the question: We have grouped data and need the mean. For grouped data, we use the class midpoint of each class as its representative score. Concept: Mean = Σfx / Σf, where x is the class midpoint and f is the frequency. Solution: | Score | Midpoint (x) | Frequency (f) | fx | |-------|-------------|---------------|-----| | 0 - 4 | 2 | 2 | 4 | | 5 - 9 | 7 | 1 | 7 | | 10 - 14 | 12 | 2 | 24 | | Total | | 5 | 35 | Midpoints: (0+4)/2 = 2, (5+9)/2 = 7, (10+14)/2 = 12 Mean = 35 / 5 = 7.0 Answer: Option D, 7.0. Tip: Check whether the frequencies are symmetric about the middle class. Here they are 2, 1, 2, so the mean must be the middle class midpoint, 7. You can get the answer without any calculation.

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