6.7 Refer to the previous exercise. Table 6.16 shows output for a cumulative logit model with scores {1, 2, 3} for the income categories.

a. Explain why the output reports two intercepts but one income effect.

b. Interpret the income effect.

c. Report a test statistic and P-value for testing that marital happiness is independent of family income. Interpret.

d. Does the model fit adequately? Justify your answer.

e. Estimate the probability that a person with average family income reports a very happy marriage.