Table 7.19 refers to a clinical trial for the treatment of small-cell lung cancer. Patients were randomly assigned to two treatment groups. The sequential therapy administered the same combination of chernotherapeutic agents in each treatment cycle; the alternating therapy had three different combinations, alternating from cycle to cycle.

a. Fit a cumulative logit model with main effects for treatment and gender. Interpret.

b. Fit the model that also contains an interaction term. Interpret. Does it fit better? Explain why it is equivalent to using the four gender €“ treatment combinations as levels of a single factor.

Table 7.19:

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Response to Chemotherapy No Partial Progressive Complete Remission 26 2 20 1 Therapy Sequential Gender Male Female Male Female Disease 28 4 Change 45 12 Remission 29 Alternating 41 12 44 20 3