Question 1132191
.
<pre>

  The probability that at most 11 of the 13 babies are girls =


= the COMPLEMENT to the probability that all babies are girls or 12 babies are girls = 


    = 1 - {{{1/2^13}}} - {{{C[13]^12*(1/2^12)*(1/2)}}} = 1 - {{{1/8192}}} - {{{13/8192}}} = 0.9983 = 99.83%.
</pre>