Many women take oral contraceptives to prevent pregnancy. Under ideal conditions, 1% of women taking the pill become pregnant within one year. In typical use, however, 5% become pregnant. Choose at random 20 women taking the pill. How many become pregnant in the next year?
a) Explain why this is a binomial setting.
b) What is the probability that at least one of the women becomes pregnant under ideal conditions? What is the probability in typical use?