Hypertension has often been claimed to aggregate in families. That is, if 1 person in a family is hypertensive, then his or her siblings are more likely to be hypertensive. Suppose the prevalence of hypertension among 50- to 59-year-olds in the general population is 18%. Suppose we identify sibships of size 3 in a community where all members of the sibship are 50 to 59 years old.
1. What is the probability that 0, 1, 2, or 3 hypertensives will be identi ed in such sibships if the hypertensive status of 2 siblings in the same family are independent events?
2. Suppose that among 25 sibships of this type, 5 have at least 2 a ected siblings. Are these data consistent with the independence assumption?