Intended for healthcare professionals

Endgames Statistical question

Conditional probabilities

BMJ 2009; 338 doi: (Published 15 January 2009) Cite this as: BMJ 2009;338:b113
  1. John Fletcher, clinical epidemiologist
  1. 1BMJ, London WC1H 9JR
  1. jfletcher{at}

    Mike has only two children, and they are called Pat and Alex, which could equally be boys’ or girls’ names. In fact, Pat is a girl. What is the probability that Alex is a boy?

    • a 50%

    • b Slightly less than 50%

    • c Slightly more than 50%

    • d Between 60% and 70%

    • e Between 40% and 30%


    d—Although this could be …

    View Full Text

    Log in

    Log in through your institution


    * For online subscription