NYE Babies
Posted in Uncategorized on September 29th, 2011To those doubting my theory about NYE babies, I checked all 12 months for number of births of friends on Facebook (a sample taken from 512 friends). I focused on the range of the 25th to the 5th, as some people are a few days early, and some are a few days late. So for example, for NYE, I checked the range 25 Sep to 5 Oct. So what did I find exactly?
10 of the months I checked had a max of 14, a mean of 12.1 births in that range, a median of 13, a mode of 13, and a standard deviation (stddev) of 1.8. This implies that the max is easily within two stddevs of the mean, and really close to being within 1 stddev of the mean (both are significant facts). Now, let’s also think about this from another angle. Let’s say people are equally likely to be born on any day of the year. 512 people divided 365 days is 1.4 birthday per day. Spread that out over a 9-11 day period, and you get between 12.6 and 15.4 birthdays in those ranges. Most of the 10 months fall within 1 stddev of this range, meaning 10.8-17.2 (1 month had 9 births, another had 10 births). Again, this seems to point to the fact that 10 months out of the year, birth rates appear to be normal.
But what was the number I found for those suspected of being NYE babies? Did it follow this same trend? No, the number I found was 19. That’s almost 4 stddevs away from the mean. That’s also 0.3 births/day more than should be expected, assuming every day is equally likely to see the same number of births. Again, this number is statistically significant. I then decided to check another holiday: Valentine’s Day. Nine months later, +/- 5 days would be 9-19 Nov. I was actually a bit surprised to see the number was only 13. What does that mean? Well, your guess is as good as mine, but I think that couples are expecting a certain something on Valentine’s Day and are prepared for it. On NYE, they might not be, or are too inebriated from the festivities to care.
But wait! If you read carefully what I wrote above, you’ll notice that I said 10 of the months, not 11. Why did I exclude one? Well, there’s another event that happens on the last day of a month: Halloween. And what happens on Halloween in America? Parties. Apparently a lot more happens *after* those parties. How do I know, you ask? Well, if we fast forward nine months from Halloween, we get a range of dates from 25 Jul to 5 Aug. How many people were born in that range, you ask? 23! Yes, that’s right, 23. That’s nearly 5% of my contacts on Facebook as opposed to the 3% that it should be, or the 3.7% from NYE.
Just food for thought.





