Calling all mathmagicians - what are the odds?

[Indistinguishable]

Of course, all odds are only defined relative to some supposed (alternative or counterfactual) distribution. If the real-world distribution you’re really interested in is “Out of all the 9-worker offices in the world currently, how many…”, there’s nothing to do but actually gather the data on all the 9-worker offices in the world currently. For various purposes, various approximations to that count might suffice, but the purpose here in getting exact odds beyond “Is this surprising or not?” is probably purely recreational, rather than a problem of any intended application.

[LSLGuy]

@septimus

Nitpick: Setting aside February 20, calculations assume that the 365 dates are equally likely for birth. This is not the case. In the U.S., births peak in summer and early autumn, and are lowest in springtime.

A study of several hundred thousand insurance applicants found dates in September to be 12% more common than dates in April. Perhaps it’s **climatic differences **nine months prior that explain this.

Bolding mine.

Nine months prior to September is December. Old Saint Nick should perhaps be renamed Old Saint KnockHerUp.

[Tim_T-Bonham.net]

@LSLGuy

Nine months prior to September is December. Old Saint Nick should perhaps be renamed Old Saint KnockHerUp.

I once ick’d out my siblings by pointing out that our birthdays were 9 months after Valentines Day, 9 months after St. Patricks Day, and 9 months after our parents Wedding Anniversary.

[Mean_Mr.Mustard]

@t-bonham@scc.net

These calculations are also inaccurate in assuming the the ‘9 people in my office’ are a random, independent group. But that’s unlikely to be true in msny offices.

In a small office, there might be several people from the same family. Birthdates tend to cluster together in families. (Especiaslly pre-birth control. There were several families in my grade school how had multiple children born in the same month of the year.)

Also, office groups are often about the same age. And similar race & ethnic groups. Those could also lead to non-random birthdates.

I think my 9 are a pretty random group, aside from the fact that we all have the same type of schooling/occupation and we all live in the same general area of the U.S.

mmm

[igor_frankensteen]

@septimus

Nitpick: Setting aside February 20, calculations assume that the 365 dates are equally likely for birth. This is not the case. In the U.S., births peak in summer and early autumn, and are lowest in springtime.

A study of several hundred thousand insurance applicants found dates in September to be 12% more common than dates in April. Perhaps it’s climatic differences nine months prior that explain this.

Thankyou. This kind of thing is why I have come to squint suspiciously every time someone proclaims that the odds of such-and-such are whatever. It’s not that I distrust the math, it’s that I distrust the sometimes hundreds of assumptions made BEFORE the calculations are done.
This is also why we live in an age of a plague of false “statistical correlations.”

[ftg]

@Indistinguishable

You keep saying 356 where you mean 365. But, yes.

There’s also septimus making an exception for Feb. 20th for some reason.

Maybe there’s a rule that in any thread on numbers there has to be trivial numeric typos.

[bob_2]

While not wishing to correlate unrelated statistics, it would seem reasonable to assume that the Christmas period, with high alcohol use, extended holidays (many in the UK are off from Christmas Eve to Jan 3rd), and restricted access to doctors and pharmacies, is directly linked to the peak in births at the end of September.

If three people in a group of nine shared a January or February birthday, that would be far more improbable that if it was in September/October.

[LSLGuy]

@t-bonham@scc.net

I once ick’d out my siblings by pointing out that our birthdays were 9 months after Valentines Day, 9 months after St. Patricks Day, and 9 months after our parents Wedding Anniversary.

The two sets of people on earth who don’t have sex are your parents and your children.

September baby here. :eek: