Quantcast XP Math - Forums - View Single Post - What is the probability that all 9 babies will be boys in regards to probability?
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Old 07-25-2007   #7
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The male to female birth ratio is not 1 to 1. The answers above all assumed there was an equal chance of a boy being born as of a girl. The source I quote below shows the *** ratios for most countries of the world. In the USA, for example, the ratio is 1.05 male births for every female birth. This means 1.05/(1.05+1)=1.05/2.05=0.5122 = 51.22% of babies born in the USA are male, NOT 50.00%.If we take 9 random births, say the next 9 babies born in the USA, then the probability that all are males is 0.5122^9, or about 0.24%.Genetic experts might argue that if the question was for a particular family then after a few boys in a row it might show that the father and mother or their environment is making it more likely than normal that the next baby will again be a boy.But for the general population, in the USA, the answer is about 0.24%.