UPSC NDA Math Model Paper 7

Given two lines of regression,
x + 3y = 11
⇒ y = 11/3 − x/3
So, byx = − 1/3
Again,
2x + y = 7
⇒ x = 7/2 - y/2
So, bxy = −1/2
{ Coefficient of correlation =‌√byx×bxy=‌√

−1

3

×

−1

2

=‌√

1

6

=‌0.408
Since bxy‌and‌byx are negative.
r = −0.408
Note: If bxy‌and‌byx are negative then coefficient of correlation would be negative and if If bxy‌and‌byx are positive then coefficient of correlation would be positive.Q