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NDA 2024 Maths · Mathematics · Statistics · medium

The variance of the observations 1,3,5,7,9,11 is

Single correct option

The variance of the observations 1,3,5,7,9,111,3,5,7,9,11 is
  1. A. 7070
  2. B. 1414
  3. C. 356\frac{35}{6}
  4. D. 353\frac{35}{3}
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Answer: (D) 353\frac{35}{3}

The mean is 366=6\frac{36}{6}=6. The squared deviations are 25,9,1,1,9,2525,9,1,1,9,25 with sum 7070. The variance is 706=353\frac{70}{6}=\frac{35}{3}. Trap: 70 is the sum of squared deviations, 14 divides by n−1=5n-1=5, and 356\frac{35}{6} divides by 2n2n by mistake.
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Original question written in the NDA 2024 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake