6.50 Binomial needs fixed n For the binomial distribution, the number of trials n is a fixed number. Let X denote the number of girls in a randomly selected family in Canada that has three children. Let Y denote the number of girls in a randomly selected family in Canada (that is, the number of children could be any number). A binomial distribution approximates well the probability distribution for one of X and Y, but not for the other.

a. Explain why.

b. Identify the case for which the binomial applies and identify n and p.