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Thursday, June 4, 2015

"What are the odds?" That 3 People are Born at the Same Time (6:23 AM)

I assumed that births are not evenly distributed throughout the day, and found this to be the case, according to "The Hour of Birth: A Study of the Distribution of Times of Onset of Labour and Delivery Throughout the 24-Hour Period" by Enid Charles (which was referred to by this RJ Metrics article, which tackled a similar question regarding births at a given time of day). This study found that births are indeed not evenly distributed:



4.5% of births occur during the hour of 6 am, and, if we assume a uniform distribution across the minutes of an hour, the probability of being born at exactly 6:23 am is 4.5% * (1/60) = 0.075%. To clarify whether the two kids are twins, they are not:


So this means each birth time was independent. 
For 3 people, 0.075%3 = 0.0000000421875%, or roughly 1 in 23,703,700.

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