Clarke Ching's Rocks and Snowballs

Twins

A guy I used to work with just sent an email out saying that his wife
had just delivered twins. One of the babies was born 2 minutes before
midnight; the other at 4 minutes past.

They're twins but they have different birthdays!

How cool is that!

-oOo-

But more important: how unusual is that?

Now heres the thing. I'm re-reading Hubbard's How To Measure Anything
and it got me wondering. One his first examples is trying to estimate,
during the 1930s, how many piano tuners there are in Chicago. (It came
from a famous scientist whose name I can't recall.) He takes the
reader through a few questions, breaking down the question into
smaller questions which can be answered - estimated population,
estimated number of pianos, estimated frequency a piano gets tuned,
and so on - then rolls those answers up to come up with a range of
possible answers. I think the range was between 20 and 200 which might
not sound precise but it is a helluva lot more useful than "dunno".
The answer, when checked against a telephone book, was about 50.

So I'm wondering. If I wanted to estimate how unusual or common it was
to have twins with different birthdays, where would I start?

I'm not going to show my working here but if you feel like adding a
comment go for it.

Bee ewe em

My 5 year old daughter, Alice, told us at  lunch today, "No one else in my class knows how to spell bum".

Which made me proud.  

But then I wondered, how does she know with such certainty that none of the others can spell it?  

Hushed conversations must have been had.

Then  my other daughter, the 8 year old, Aisling, said, 'I taught her how to spell it.'

Which made me even prouder.  

Because I taught Aisling how to spell it.