Skip to content

CA Foundation · Quantitative Aptitude · Correlation and Regression

The two regression lines of a data set are 4x − 5y + 20 = 0 and 20x − 9y = 92. Taking the first as the regression of y on x and the second as the regression of x on y, what is the correlation coefficient between x and y?

The correlation coefficient is +0.60. The regression coefficients are b_yx = 0.8 and b_xy = 0.45, so r² = 0.36 and r = 0.6. Since both coefficients are positive, r is positive. The value 0.36 is only r squared.

  1. A0.60Correct
  2. B0.36
  3. C0.80
  4. D−0.60

Explanation

From the first line, y = 0.8x + 4, so b_yx = 0.8. From the second, x = (9/20)y + 4.6, so b_xy = 0.45. Then r² = 0.8 × 0.45 = 0.36, so |r| = 0.6. Both coefficients are positive, so r = +0.60. The value 0.36 is r², not r.

Did you get it right without looking?

One question tells you little. A timed set on Correlation and Regression shows your real accuracy, how long you take and where you lose marks.

Practise Correlation and RegressionFree diagnostic mock

More Correlation and Regression questions