There is a real danger in confusing the idea of causation with that of statis¬

tical association. Why do you think these two concepts are so often confused?

For example, for centuries it was thought that swampy air when breathed

“caused” malaria (hence the name, literally “bad air”). Comment on what this example shows about statistical association and causation.

39.For the distribution of Exercise 2, find the correlation coefficient of X and Y = (X - 3)2. In this example, if we know X, we can easily determine F with certainty, and vice versa. If this is true, why is the correlation coeffi¬

cient not equal to +1 or —1? What does this example illustrate about cor¬

relation and association?

40.If cov (X, F) = 1.0, what can we say about the relationship between X and F? If cov (Z, W) = 2.0, does this mean that the relationship between Z and W is stronger than the relationship between X and F? Explain.