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CA Foundation · Quantitative Aptitude · Correlation and Regression

In 11 observations of two series, no pair of deviations has the same direction, so c = 0. What is the coefficient of correlation by the concurrent deviation method?

The coefficient is −1. With 11 observations n = 10, and c = 0 gives 2c − n = −10. Hence r = −√(10/10) = −1, showing every change in one series is matched by an opposite change in the other.

  1. A0
  2. B-1Correct
  3. C+1
  4. D-0.5

Explanation

n = 10 pairs of deviations and c = 0. Then 2c − n = −10, which is negative, so r = −√(10/10) = −1. The series always move in opposite directions, so the correlation is perfectly negative in this method.

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