The likelihood of exactly 90 girls in 200 births is 0.0208. Since this probability is lower than 0.05, this is an unlikely event. To see whether 90 girls is an unusually low number of girls, we need to think about the probability of having 90 or fewer girls. Since P(90 or fewer girls) = 0.089>0.05, this is not an unusually low number of girls.