In a study of patients who had undergone surgery of breast cancer, 81 out of 306 have died within 5 years (Haberman, 197

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In a study of patients who had undergone surgery of breast
cancer, 81 out of 306 have died within 5 years (Haberman, 1976).
These 81 patients had on average 7.5 positive axillary nodes
detected, while the 225 patients who survived 5 years or longer had
on average 2.8 nodes detected. Let us assume that within each group
the number of positive axillary nodes follows a geometric
distribution. Estimate probability of survival within 5 years for a
patient with 2 positive axillary nodes detected.