# Math Geek Mom: Probabilities and Possibilities

Last week, as classes started, I performed an experiment that I always use on the first day of each of my classes in statistics.

## By

September 3, 2009

Last week, as classes started, I performed an experiment that I always use on the first day of each of my classes in statistics.

I use the fact that everyone in the world must share one of only 365 birth days (366, if you count leap years). This therefore implies that the chances of finding, in a group, two people who share a birth date is actually quite high. In fact, people who have used this information to calculate the probability of such a match have found that the probability of having at least one match in a room with about twenty people in it are greater than 50%. I use this as a starting point for my statistics classes, and proceed to see if there are any matches among my students. There almost always is, and often I find two or more matches.

Last week, however, I found none. The last time that happened, I proceeded to my next class, a small, “majors” class, where, among the five students there, I found a match. This time, however, there was no match to be found, not even in my small, majors classes. It was as if the semester began to the theme song of “Twilight Zone”. Would this be a semester in which all bets were off, where we could not trust probabilities to predict the world for us? I recalled the play of “Rosencrantz and Guildenstern are Dead”, where a coin is flipped many times, continuously coming up as “heads”. Was our new semester to be just as absurd?

Perhaps, or perhaps this just means that this semester brings with it not just new probabilities, but new possibilities, too. I recall a theology professor I had in college who was fond of the phrase “new possibilities”, and I hope, as this semester gets under way, that this strange occurrence in my statistics class is simply an indication of the new possibilities that this new school year brings to us. I remember that this professor not only liked to say the phrase, she lived it. She was a woman professor at a university that had begun accepting women students only about 10 years earlier, and still had many on-campus institutions that clearly remembered the days when only men attended the school. She was not just a theologian, but a prominent Catholic theologian, in a church that did not have many options for leadership positions for women. And, long before I ever thought of adopting my daughter, I saw her, a middle aged academic, modeling the role of being an adoptive parent to two children who had been in need of homes. Indeed, her whole life was one of “new possibilities” which she modeled to her students.

And so, as the semester gets underway, with or without a “birthday match”, I wish everyone the best as we set off on our new adventure, one filled with, if not matching birthdates, at least many “new possibilities”.

+ -