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AP EAMCET · Maths · Statistics

The mean deviation of the numbers \(a, a+d, a+2 d, \ldots, a+2 n d\) from their mean is equal to

  1. A \(\frac{(n+1) d}{2 n+1}\)
  2. B \(\frac{n(n+1) d}{2 n+1}\)
  3. C \(\frac{(n+1)|d|}{2 n}\)
  4. D \(\frac{n(n+1)|d|}{2 n+1}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\frac{n(n+1)|d|}{2 n+1}\)

Step-by-step Solution

Detailed explanation

\(\bar{x} = \frac{a + (a+2nd)}{2} = a+nd\) \(\sum |x_i - \bar{x}| = 2 \sum_{k=1}^{n} |a+kd - (a+nd)| = 2 \sum_{k=1}^{n} |(k-n)d|\) \(= 2|d| \sum_{k=1}^{n} |k-n| = 2|d| \sum_{j=1}^{n} j = 2|d| \frac{n(n+1)}{2} = n(n+1)|d|\) \(N = 2n+1\)…