For parts (a)-(c) suppose that each twin in the pair is equally likely to die first, regardless smoking or not. So the n

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For Parts A C Suppose That Each Twin In The Pair Is Equally Likely To Die First Regardless Smoking Or Not So The N 1 (353.13 KiB) Viewed 61 times

" 6. It is now generally accepted that cigarette smoking causes heart disease, lung cancer, and many other dis- eases. However, in the 1950s, this idea was controversial. There was a strong association between smoking and ill-health, but association is not causation. R. A Fisher advanced the “constitutional hypothesis: there is some genetic factor that disposes you both to smoke and to die. To refute Fisher's idea, the epidemiologists used twin studies. They identified sets of smoking-discordant monozygotic twin pairs. “Monozygotic” twins come from one egg and have identical genetic makeup; “smoking-discordant” means that one twin smokes, the other does not. The researchers collected data on which twin dies first, the smoker or the non-smoker. The data from a Finnish twin study are shown in the following table. All Causes Coronary heart disease Lung Cancer Smokers Non-smokers 17 5 9 0 2 0 According to the first line of the table, there were 22 smoking-discordant monozygotic twin pairs where at least one twin of the pair died. In 17 cases, the smoker died first; in 5 cases, the non-smoker died first.