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JAMB Mathematics 1992 Question 46

Question 46

Measures of Dispersion

Sample variance can be defined as S2 = (1/n) Σ (xi − x̄)2 and S2 = (1/(n − 1)) Σ (xi − x̄)2 where n is the number of sample observations. There is no difference practically between the above definitions when

  1. A.n ≠ 35
  2. B.n > 35
  3. C.n < 35
  4. D.n = 5
Show the answer and explanation

Answer: B (n > 35)

Explanation

Dividing by n or by n − 1 gives almost the same result when n is large, so the two definitions agree in practice for large samples (n > 35 here).