Interestingly enough, couples who already have two children of the same sex are around 75% more likely to have the same sex baby again. We had two boys already, so our chances of having a girl were 25%.
The chance of having a girl after two boys was about 48 per cent and the chances of having a boy after two girls was slightly lower, at only 46 per cent. So you are more likely to have the same gender when you already have two of the same.
Couples with 3 children: 25% of couples have 3 girls or 3 boys, and 75% have 1 boy/2 girls or 1 girl/2 boys. Couples with 4 children: 12.5% of couples have 4 girls or 4 boys, 37.5% will have 1/3 and 50% will have 2/2.
Elementary probabilities: If someone has a single child, the probability that it is a male is 0.5. If someone has two children, the probability that they are both males is 0.5*0.5 = 0.25. If someone has three children, the probability that they are all males is 0.5*0.5*0.5 = 0.125.
If you have two children, you'll have a 50% chance of having a second boy, based on the ratios above. Then if you have three children, you'll have a 25% chance of having all three boys, and a 75% chance of two girls and a boy or two boys and a girl.
Would we have a third? In terms of having another boy or girl , the odds of having another boy after two boys is only slightly more than having a girl. Even after two boys, you are only 2.3 per cent more likely to have a third boy than a girl.
My general response is that it's a 50/50 chance that a woman will have a boy or a girl. But that's not exactly true – there's actually a slight bias toward male births. The ratio of male to female births, called the sex ratio, is about 105 to 100, according to the World Health Organization (WHO).
We might expect that naturally an equal number of boys and girls are born, but this is not the case. There are biological reasons why more boys than girls are born each year: around 105 boys per 100 girls. But in countries with a strong son preference, the sex ratio is even more skewed.
And as we can see, for 3 of the 8 states the function evaluates to 2. This means that after counting all possibilities, we found that 3 of the 8 equiprobable states correspond to two boys. This gives a probability of 38.
According to the binomial expansion, the probability of 3 boys and 1 girl will be 4a3b where 3 is an exponent. So we get.... 4(1/2)^3 (1/2) = 4/16 = 1/16.
Dr Brendan Zietsch from UQ's School of Psychology said the study was the largest conducted on the often-debated question, and concluded the sex of offspring is essentially random. “We found individuals don't have an innate tendency to have offspring of one or the other gender,” Dr Zietsch said.
Refining the probability a little bit, there are about 105 boys born for every 100 girls, so about 51.2 percent of babies are boys. The probability, then, of 14-boy families among all 14-child families, is (. 51214), which is about 0.0085 percent.
Thus, the correct answer is '1/16. '
Doing the math, the odds of having the same gender children (all boys or all girls) comes out to 50 percent if you have a total of two children, 25 percent if you have three children, and it keeps cutting in half as you increase family size by one child when computing the odds.
While historically, there have been about 105 boys born for every 100 girls worldwide — which creates a “sex ratio at birth” of 1.05 — the share of boy babies has increased in recent decades.
Who Determines the Sex of the Baby? Perhaps you've wondered which parent determines the gender of the child? It takes two to tango, but scientifically, it only takes the sperm to determine the baby's sex. The egg will always have an X chromosome, so it's up to the sperm to decide.
Next, the technician would locate the genital tubercle protruding from between baby's legs and determine the angle between the nub and the fetal spine. If the nub angle is more than 30 degrees, baby is likely a boy. If the nub is parallel to the spine and less than 30 degrees, baby is likely a girl.
The Odds of Getting Pregnant
For most couples trying to conceive, the odds that a woman will become pregnant are 15% to 25% in any particular month.
Conclusion. The Chinese birth calendar claims 93-99% accuracy in predicting infant gender based on month of conception and maternal age at delivery. In this large delivery dataset, accurate prediction of fetal gender based on the Chinese birth calendar was no better than a coin toss.
Have sex regularly. The highest pregnancy rates occur in couples who have sex every day or every other day. Have sex near the time of ovulation. If having sex every day isn't possible — or enjoyable — have sex every 2 to 3 days a week starting soon after the end of your period.
If you ask “for any family with two children, what are the chances that they have one boy and one girl” the answer is 50% (and a 25% there are two boys and 25% that there are two girls).