✔ 最佳答案
(a) Using "M" and "F" for indicating male and female children, we have, for a family having 3 children, the possible sequences of the genders of the children are:
MMM
MMF
MFM
FMM
MFF
FMF
FFM
FFF
Therefore, counting all the above possibilites, we can construct the Probability Mass Function as follows:
P(X) = 1/8, if X = 0 or 3
P(X) = 3/8, if X = 1 or 2
P(X) = 0, otherwise.
(b) From the result of (a), the probability that exactly one female child is 3/8.
(c) From the result of (a), the probability that at most one female child is 1/8 + 3/8 = 1/2.
(d) From the result of (a), the probability that at least one female child is 1 - 1/8 = 7/8.
