Refer to Problem 15.6. For marginal homogeneity, explain why the minimum modified chi-squared estimates are identical to WLS estimates.

Data from Problem 15.6:

Consider marginal homogeneity for an I × I table.

a. Letting F(π) = Aπ, explain how (i) F(π) = 0, where A has I – 1 rows, and (ii) F(π) = Xβ, where A has 2(I – 1) rows and β has I – 1 elements. In part (ii), show A, π, X, β when I = 3.

b. Explain how to use WLS to test marginal homogeneity. [This is

Bhapkar’s test (10.16).]