Anonymous wrote:Regarding twins in the LAMB lottery results, in PK3 in particular (I didn't look at PK4):
Some twins are named twice, with their sibling, with the two names listed in reverse order. So, "A & B Lastname" and "B & A Lastname," as two separate entries. There are seven pairs like this. That's sort of a clever way to distinguish twins from unrelated kids with common last names.
There are nine pairs of adjacent entries with the same last name, but without any second first name mentioned. Odds are small that two unrelated kids with the same last name would happen to land in the ranking next to each other. So, presumably they're pairs of twins (the higher-ranked sibling pulled up the lower-ranked sibling). Curiously they are all in the top 95. Nowhere in the other 449 was there a pair of adjacent entries with the same last name.
Further, there are six entries of the form A+B but for which there is no matching B+A entry. We can presume these represent six more pairs of twins, but for whatever reason, they did not enter the second child in the lottery.
So, counting up all the twins... We have 7 + 9 + 6 = 22 pairs of twins, or 14 + 18 + 6 = 38 children who are twins (since the six didn't bring their twin to the party)
According to the CDC (http://www.cdc.gov/nchs/data/databriefs/db80.pdf):
The twin birth rate in the United States rose 76% from 1980 through 2009, from 18.9 to 33.3 per 1,000 births.
According to those numbers, one would expect the 544 LAMB PK3 applications to include approximately 18 twins. Instead, there are 38 twins, more than double the expected number. So, whoever fired off his/her mouth about the number of twins had a point about the prevalence of twins.
There are two "cheater" entries which each represent a child entered twice. #44/45 and #46/47 are both also listed together further down the list: #151 and #534. For each of those two cases, the twins have three entries between them: A, B, and A+B (so A entered twice). Cheating seems to have paid off; both are ranked highly.
There is one case of: A+B and B, but that just means B forgot to mention A. (this case is included in the nine)
It's unclear why there are six A+B entries that are lacking a B+A entry. None of those entries are ranked well. For their sake, hopefully those families didn't forget to enter twice.
Overall, twins faired better than single kids. Almost half the twins (18 of the 38) and in the top 95 (the top 17% of the whole population). This is to be expected, since essentially each twin has two ways to win (either get a good ranking themselves or hope their sibling does).
So, hooray for being twin and double-hooray for the two families who cheated (a little). Classic DC, lots of twins and a few cheaters.