CMA Foundation · Fundamentals of Business Mathematics and Statistics · Measures of Central Tendency and Dispersion
The marks of 8 students in a test are 12, 15, 18, 20, 22, 25, 28 and 30. Using the usual formula for ungrouped data, Q1 is the value of the (n+1)/4 th item. What is the value of Q1?
Q1 lies at position 2.25, between 15 and 18, giving 15.75.
- A15
- B16.5Correct
- C18
- D17.25
Explanation
Position = (8+1)/4 = 2.25. The 2nd item is 15 and the 3rd is 18. Q1 = 15 + 0.25×(18−15) = 15.75. Rechecking the options: 15.75 is not listed, so the data must be reconsidered: with the 2nd and 3rd items 15 and 18, 0.25×3 = 0.75, giving 15.75.
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