CA Foundation · Quantitative Aptitude · Correlation and Regression
Two series each have 13 observations. The concurrent deviation method gives a coefficient of correlation of +√(1/3). How many pairs of deviations have opposite directions?
Four pairs have opposite directions. With 13 observations n = 12. Setting (2c − 12)/12 = 1/3 gives c = 8 concurrent pairs, so the pairs moving in opposite directions number 12 − 8 = 4.
- A3
- B8
- C6
- D4Correct
Explanation
n = 13 − 1 = 12. Squaring, (2c − n)/n = 1/3, so 2c − 12 = 4 and c = 8. Opposite-direction pairs = n − c = 12 − 8 = 4. The value 8 is the number of concurrent pairs, not opposite pairs.
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