The Health Examination Survey used a nationwide
probability sample of people
between age 18 and 79 from the United States civilian, noninstitutional
population. The participants were asked to complete a self-administered
questionnaire. The sample contained 4211 females, of whom 3581 completed
the questionnaire. We restrict attention to the age range 25-59 years.
Furthermore, seven women who were less than 35 years of age and reported
having had a natural menopause were excluded as being an error
or abnormal. The remaining data set contains information on 2423 women.
MacMahon and Worcestor (1966) found that there was
marked terminal digit clustering in the response of this question,
especially for women who had a natural menopause.
Therefore, Krailo and Pike (1983) decided to only consider the menopausal
status of women at the time of the questionnaire, yielding current
status data on the age of menopause with two competing
risks: operative menopause and natural menopause.