The two regression lines become identical if the correlation coefficient is ans. 0 ±1 2 none

Analysis of the Problem

To determine when two regression lines become identical, we need to examine the relationship defined by the correlation coefficient $r$.

Relevant Concepts

1. The regression line of $Y$ on $X$ is given by $Y = a + bX$.
2. The regression line of $X$ on $Y$ is given by $X = c + dY$.
3. When the two regression lines are identical, it means the slope and intercepts result in the same line.

Key Points on Correlation Coefficient

• The correlation coefficient $r$ can take values between $-1$ and $1$.
• If $r = 1$ or $r = -1$, the data points lie perfectly on a line, which means both regression lines will be identical.

Final Answer

The two regression lines become identical if the correlation coefficient is $\pm 1$.