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If the two regression lines are as under :
Y = a + bX
X = c + dY
What is the correlation coefficient between variables X and Y?
  • a)
    √bc
  • b)
    √ac
  • c)
    √ad
  • d)
    √bd
Correct answer is option 'D'. Can you explain this answer?
Most Upvoted Answer
If the two regression lines are as under :Y = a + bXX = c + dYWhat is ...
The correlation coefficient between variables X and Y can be calculated using the formula:

r = √(bd)

Since the regression lines are given as:

Y = a + bX
X = c + dY

We can rearrange the second equation to solve for Y:

Y = (X - c)/d

Substituting this value of Y in the first equation, we get:

Y = a + b((X - c)/d)

This can be simplified as:

Y = (ad + bc - bd)/d

Now, we can equate this expression to the original equation for Y:

(ad + bc - bd)/d = a + bX

Rearranging the equation, we get:

ad + bc - bd = ad + bd + b^2X

Simplifying further, we have:

bc = b^2X

Dividing both sides by b, we get:

c = bX

Now, substituting this value of c in the equation X = c + dY, we get:

X = bX + dY

Rearranging the equation, we have:

Y = (X - bX)/d

Simplifying further, we get:

Y = (1 - b)/d

Now, we can substitute these values of X and Y in the correlation coefficient formula:

r = √(bd)

Substituting the values of b and d, we get:

r = √(b(1 - b))

Therefore, the correlation coefficient between variables X and Y is √(b(1 - b)).
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Community Answer
If the two regression lines are as under :Y = a + bXX = c + dYWhat is ...
Y = a + bX
Where, a and b are constants
b = it is called the regression coefficient of Y on X and is denoted by byx. It measures the change in Y corresponding to a unit change in X.
Thus, byx = Slope of the line of regression of Y on X = b
X = c + dY
where, c and d are constants
d = it is called the regression coefficient of X on Y and is denoted by bxy. It measures the change in X corresponding to a unit change in Y.
Thus, bxy = Slope of the line of regression of X on Y = d
Correlation coefficient = √byx bxy
⇒ √bd
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If the two regression lines are as under :Y = a + bXX = c + dYWhat is the correlation coefficient between variables X and Y?a)√bcb)√acc)√add)√bdCorrect answer is option 'D'. Can you explain this answer?
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