CA Foundation P3 · Chapter 16 · Question 7 of 9
For a normal distribution with standard deviation 15, the mean deviation about the mean is approximately (use the conventions MD ≈ 0.8σ and QD ≈ 0.675σ):
Test yourself: pick an answer
Reveal answer & explanation
Correct answer: A) 12
Explanation
For a normal distribution, mean deviation ≈ 0.8σ (more precisely √(2/π)σ ≈ 0.7979σ). MD ≈ 0.8 x 15 = 12. Quartile deviation ≈ 0.675σ = 0.675 x 15 ≈ 10.1, so 10 is the QD, which is the usual confusion; 18.75 results from dividing by 0.8 instead of multiplying, and 15 is σ itself.
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