WAEC Mathematics 2013 Objective — Question 27

Question 27 of 50 from the West African Examinations Council (WAEC) Mathematics 2013 Objective paper, with the correct answer and a full explanation.

Given that the mean of the scores 15, 21, 17, 26, 18 and 29 is 21. Calculate the standard deviation of the scores.

Explanation

Standard deviation = √(Σ(x−x̄)²/n) = √[((15−21)²+(21−21)²+(17−21)²+(26−21)²+(18−21)²+(29−21)²)/6] = √[(36+0+16+25+9+64)/6] = √(150/6) = √25 = 5.

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