May 29, 2014

Strawberries and watermelons

Teachers are usually happy to stop lecturing and have their students work on some practical exercise, and I am no different.  I teach students about sampling wildlife populations, and there is a favorite exercise that involves pretending that a pot of dried beans is a wildlife population.  The students then sample the wildlife population and attempt to determine something about it.  Sometimes, we use mark-recapture (using a marker to mark the beans) to estimate how many beans we have.  Or, we might mix black and white beans and try to estimate the proportion of black beans in the population.

I've had some interesting experiences with this exercise, especially when I used it in Namibia (students ate the beans).

I'm currently teaching on the outskirts of Bangkok, Thailand at King Mongkut's University.  It turns out that I'm too far from any store to go buy beans, so my students solved the problem for me.  They went and bought two bags of flavored candies.  100 candies in each bag.  Enough for 4 groups to have 50 pieces of candy with a mixture of the two colors.  When we were done pretending that the watermelon-flavored ones (green ones) were animals with a disease (we wanted to estimate the proportion of the population with a disease---and we wanted to see how few samples we could take to do it efficiently), we ended up eating the exercise, once again.

I like this trend!

Students work on their population sampling exercise, after living through
my lecture on maximum likelihood estimation.

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