Question

In a 1974 dear abby letter a woman lamented that she had just given birth to her eighth child, and all were girls! her doctor had assured her that the chance of the eighth child being a girl was only 1 in 100.
a.what was the real probability that the eighth child would be a girl?
b.before the birth of the first child, what was the probability that the woman would give birth to eight girls in a row?

Answer 1

Part A:

Given that In a 1974 "Dear Abby" letter a woman lamented that she had just given birth to her eighth child, and all were girls! her doctor had assured her that the chance of the eighth child being a girl was only 1 in 100.

The real probability that the eighth child would be a girl is 0.5.

There are two possibilities for the eighth child: a girl or a boy. Thus the probability that the eighth child is a girl is 1 / 2 = 0.5



Part B:

Before the birth of the first child, the probability that the woman would give birth to eight girls in a row is given by (0.5)(0.5)(0.5)(0.5)(0.5)(0.5)(0.5)(0.5) = $(0.5)^8$