WAEC Mathematics 2017 Theory — Question 15
Question 15 of 25 from the West African Examinations Council (WAEC) Mathematics 2017 Theory paper, with the correct answer and a full explanation.
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8(b) Using the value of m found in (a): (i) Find the interquartile range; (ii) Find the probability of selecting a student who scored at least 4 marks in the test.
Model answer
With m=3, the frequencies become 5,2,3,8,5 (total 23 students). (i) Q1 position=(N+1)x25%=24x0.25=6th position=2. Q3 position=(N+1)x75%=24x0.75=18th position=4. Interquartile range=Q3-Q1=4-2=2. (ii) P(score at least 4) = (8+5)/23 = 13/23 ≈ 0.565.
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