Find the probability of at least 2 girls in 7 births. assume that male and female births are equally likely and that the births are independent events.
a) 0.063
b) 0.938
c) 0.773
d) 0.164

 probibility of at least 2 girls in 7 births
 = 1 - p of less than 2 girls in 7 births
 = 1 - of 0 girls - p of 1 girls 

=1 - [7 C 0](0.5)^0*(0.5)^7 - [7 C 1](0.5)^1*(0.5)^6

=1 - (0.5)^7*{[7 C 0] + [7 C 1]}

=1 - (0.5)^7*(1 + 7)
= 1 - 0.0078125 * 8
 = 1 - 0.0625
= 0.9375
hope this helps