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WAEC Further Mathematics 2007 Question 25

Question 25

Statistics

The table shows the marks obtained by two pupils in a test.
Marks: 5 − 7, 8 − 10, 11 − 13, 14 − 16, 17 − 19, 20 − 22
Freq.: 4, 7, 26, 41, 14, 8
Find the upper class boundary of the class containing the third quartile.

  1. A.13.0
  2. B.16.0
  3. C.16.5
  4. D.22.5
Show the answer and explanation

Answer: C (16.5)

Explanation

Total frequency is 100, so Q₃ is the 75th mark. Cumulative frequencies are 4, 11, 37, 78, …, so it lies in 14 − 16, whose upper class boundary is 16.5.