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CMA Foundation · Fundamentals of Business Mathematics and Statistics · Measures of Central Tendency and Dispersion

For the marks 12, 15, 18, 20, 25, 30, 32 of seven trainees at a Pune firm, the first quartile is taken as the value at position (n+1)/4 and the third quartile at position 3(n+1)/4. What is the quartile deviation?

The quartile deviation is 7.5. With seven observations, Q1 is the second value, 15, and Q3 is the sixth value, 30. Quartile deviation is half the difference between them, so (30 − 15) divided by 2 gives 7.5.

  1. A7.5Correct
  2. B15
  3. C6.5
  4. D8.5

Explanation

n = 7, so Q1 is at position 2 = 15 and Q3 is at position 6 = 30. Quartile deviation = (Q3 − Q1)/2 = (30 − 15)/2 = 7.5. The value 15 is the inter-quartile range, which forgets to divide by 2.

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