3. What is the z-score for the x = 58 observed cases of suicide deaths? How do you interpret this z-score in light of following comments? How safe is plastic surgery? Do breast implants reduce cancer risk? Do they increase the risk of suicide? First we consider the question: Do breast implants increase the suicide rate? Researchers combed vital statistics and death certificates of 24,558 women in Ontario and Quebec who underwent breast implant surgery from 1974 to 1989. They identi- fied 58 suicides among the 480 breast-implant recipients who died. In a comparable general female population without implants, they would have expected 33 suicide deaths. How unusual was this number of suicide deaths? That is, statistically speaking, is 58 a highly improbable number of suicide deaths in this group of women with breast implants? If the answer is yes, then either some external factor caused this unusually large number, or we have observed a very rare event! The Poisson probability distribution provides a good approximation to the distribu- tion of variables, such as the number of deaths in a region due to a rare disease, the number of accidents in a manufacturing plant per month, or the number of airline crashes per month. Therefore it is reasonable to assume that Poisson distribution provides an appropriate model for the number of suicides in this instance.