The nature of Statistics Canada's National Population Health Survey (NPHS) allows the use of event history analysis techniques to study relationships among events. The output from a series of health related questions to explore an association between pregnancy and smoking cessation was of especial interest. A methodology was proposed based on the notions of time order. In essence, the research team investigated whether one of the two events tended to precede the other closely in time. In this way, a causal interpretation of an association between these events would be more plausible.
Detecting ovarian cancer is, in general, difficult because of the lack of effective screening tests. If the disease is discovered when confined to the ovaries, surgery alone is curative in more than 90% of patients - however, in most patients, diagnosis only occurs after dissemination beyond the ovaries. In these cases, a combined treatment of surgery and chemotherapy is necessary. Unfortunately prognosis is grim and median survival is only 3 years despite treatment.