Consider the phase space that consists of elements of the form (boy, boy, boy, boy), (girl, boy, boy, boy),...,(girl, girl, girl, girl).
There is a total of 2*2*2*2=2^4=16 possible combinations and each of them has the same probability to happen. Only one element is the case we are interested in (girl, girl, girl, girl).
Therefore, the probability of a family having 4 girls is
[tex]P(girl,girl,girl,girl)=\frac{1}{16}=0.0625[/tex]
The answer is false, the probability is 0.0625
