1, 3 and 6
Correlation coefficient denoted as r tells us about the Linear Relationship between two quantitative variables. The value of r always lies between -1 and 1. It is a unit-less quantity.
If the absolute value of correlation coefficient is closer to 1 it indicates a strong Linear relationship between two variables. If the absolute value of r is closer to 0 it indicates a weak Linear Relationship between two variables.
Statement 1 is true.
Statement 2 is False as correlation coefficient has no units.
Statement 3 is true.
Statement 4 is false. As r = 0 indicates no linear relationship at all.
Statement 5 is false. The absolute value of r is close to 1 so it indicates a strong linear relationship
Statement 6 is true. Correlation does not imply causation. This means the two variable may or may not be causing each other but still be co-related.