I would like to find the correlation between two variables. It was suggested to me that two variables should be independent; otherwise it is not meaningful statistically to calculate a correlation. For example, variable is x and another is $y$ which won't be calculated from $x$, e.g., $y=ab/c+x$. $a$, $b$, and $c$ are some constant value that are the same for all $y$.
- Is what I understand correct?
- The data set is $y = P+Q+x$. $P$ and $Q$ depends on each $x$, and the same $x$ value can have different value of $P$ and $Q$. Is it meaningful to find a correlation given this data?