Problem 65P

Assume, as in Example 3h, that 64 percent of twins are of the same sex. Given that a newborn set of twins is of the same sex, what is the conditional probability that the twins arc identical?

Answer

Step 1 of 1

(a)

We are asked to find the conditional probability that the twins are identical given that a newborn set of twins is of the same sex.

Assume, as in Example 3h, that 64 percent of twins are of the same sex.

Let denote the twins being identical.

The probability of twins being identical is given by using the example 3h,

Let denote the twins being of the same sex.

The probability of twins being of the same sex is given by,

We are asked to find the conditional probability

Using Bayes’ rule we can write that

[The conditional probability of twins being of the same sex given that the twins being identical would be , since the identical twins are always of the same sex]

Hence the conditional probability that the twins are identical given that a newborn set of twins is of the same sex is