STATISTICS & PROBABILITY – Chance Graphics

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Duffy has just created a sweet set of children to help you talk about Chance with your students. What’s the chance of having a boy or a girl? Twins? Triplets? Quadruplets?

Your chance for having a boy is about 50% and 50% for having a girl. But many of you will know families that are all boys or all girls. Having all boys or all girls is almost always due to simple chance. Scientists have actually researched this topic and find that boys are 52% more likely than girls, so you really have a very slight increased chance of having a boy.

Did you know that Nigerian women enjoy the highest rate of twin pregnancies in the world? About 1 in 22 Nigerian women have twins. In 2013 there were 4475 sets of twins born in Australia, out of a total of 298 984 births. This represented about 15 in 1000 births.  And of these 15 sets of twins, about 30% are identical. So fewer than 5 in 1000 births in Australia are identical twins.

In 2015, there were 84 sets of triplets born in Australia, out of a total of 305 377 births. That’s a 26 in 100 000 chance of having triplets. And there has been a 400 percent increase in the rate of triplet births over the last 20 years. To create identical triplets, the original fertilised egg splits and then one of the cells splits again. Identical triplets occur in about one in a million pregnancies, a rare event indeed.

Did you know that the odds of conceiving quadruplets is predicted to be one in 729 000? To create identical quadruplets, one fertilised egg needs to split into 4 separate embryos. Phew.