d) P ( A ) = 1 / 2 .
Giải thích
d) \({\rm{P}}({\rm{A}}) = {\rm{P}}({\rm{B}}){\rm{P}}({\rm{A}}\mid {\rm{B}}) + {\rm{P}}(\overline {\rm{B}} ){\rm{P}}({\rm{A}}\mid \overline {\rm{B}} ) = \frac{2}{5} \cdot \frac{1}{2} + \frac{3}{5} \cdot \frac{1}{2} = \frac{1}{2}.\)
=> Đúng