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WAEC Further Mathematics 2009 Question 39

Question 39

Statistics

The ages, in years, of 5 boys are 5, 6, 6, 8 and 10. Calculate, correct to one decimal place, the standard deviation of their ages.

  1. A.3.2 years
  2. B.2.6 years
  3. C.1.9 years
  4. D.1.8 years
Show the answer and explanation

Answer: D (1.8 years)

Explanation

Mean = 35/5 = 7. Squared deviations 4, 1, 1, 1, 9 add to 16, so variance = 16/5 = 3.2 and s.d. = √3.2 ≈ 1.8.