I understand what correlation means on paper (as in: given high, positive correlation, then, if A is high, B is likely to be high, too). However, the classification into "high", "medium" and "low" correlation seems rather vague to me. I'm not quite sure what to make of it.
Could you give me intuitive, real-world examples for each level of correlation?
I'd like to understand it along the lines of "X and Y have a .4 correlation. This means knowing X to predict Y is roughly as useful as knowing today's ice cream sales when predicting the number of people drowned today" [this is completely made up]