Answer:
that one variable precedes the other in time, that the two variables are correlated and that this relationship is not spurious.
Explanation:
In <em>Experimental and Quasi-Experimental Designs for Generilized Causal Inference</em> (2002), researchers Cook and Campbell present a set of conditions that must be met in order to establish a valid causal relationship: <u>one variable precedes the other in time</u> (temporal precedence), <u>the two variables are correlated</u> (covariation), <u>and that this relationship is not spurious</u> (no third variable is present).
Bulgaria is the answer you're looking for.
Answer:
All schools are great
if I learn in 1 school for my whole life then I will say that is best
but there are many best schools
that is like you can't judge a book by its cover