PSTAT 120A Study Guide - Midterm Guide: Twin, Kikk, Step Function
27 Jan 2020
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Professors chen and myung: beyonc e is having twins! Twins come in two di erent types: identical or fraternal. Identical twins are alike genetically (including gender) and are typically very similar in appearance. Fraternal twins are genetically distinct and are not necessarily of the same gender. Suppose there is a 30% chance the beyonc e will have identical twins and that each child is a boy or a girl with equal probability, independently. (a) find the probability that beyonc e has one boy and one girl. Solution: let i be the event that beyonc e has identical twins, and let f be the event that she has fraternal twins. In each case, we have the following options: bb (event she has two boys), gg (event she has two girls), or bg (the event she has a boy and a girl). We are also told that a girl or boy is equally likely.
