54. Refer to the previous exercise. The phi-squared measure of association for 2 2 contin- gency tables has sample value Explain why this measure falls between 0 and 1, with a population value of 0 correspond- ing to independence. (It is a special case, for 2x2 tables, of the Goodman and Kruskal tau nieasure introduced in Problem 8.58 and of the r measure introduced in the next chapter.)