问题如下：
Suppose that the annual profit of two firms, one an incumbent (Big Firm, X1) and the other a startup (Small Firm, X2), can be described with the following probability matrix:
Are the returns on the two firms independent?
解释：
They are independent if the joint is the product of the marginals.
Looking at the upper left cell, 6.77% * 6.70% is not equal to 1.97%, and so they are not.
