Question

To estimate the distribution of the ages at which postmenopausal woman develop breast cancer, a sample of eight 50-year-old women were given yearly mammograms for a period of 10 years. At each exam, the presence or absence of a tumor was recorded. In the study, no tumors were detected by the women by self-examination between the scheduled yearly exams, so all that is known about the onset time of breast cancer is that it occurs between examinations. For four of the eight women, breast cancer was not detected during the 10 year study period. The age at onset of breast cancer for the eight subjects was in the following intervals: (55,56],(58,59],(52,53],(59,60], >60, >60, >60, >60. (a) What type of censoring or truncation is represented in this sample? (b) Assuming that the age at which breast cancer develops follows a Weibull distribution with parameters and , construct the likelihood function.

          To estimate the distribution of the ages at which postmenopausal
woman develop breast cancer, a sample of eight 50-year-old women
were given yearly mammograms for a period of 10 years. At each
exam, the presence or absence of a tumor was recorded. In the
study, no tumors were detected by the women by self-examination
between the scheduled yearly exams, so all that is known about the
onset time of breast cancer is that it occurs between examinations.
For four of the eight women, breast cancer was not detected during
the 10 year study period. The age at onset of breast cancer for the
eight subjects was in the following intervals:
(55,56],(58,59],(52,53],(59,60], >60, >60, >60, >60. (a) What type of
censoring or truncation is represented in this sample? (b) Assuming
that the age at which breast cancer develops follows a Weibull
distribution with parameters and , construct the likelihood
function.

Added by Robert A.

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