estimating a person's daily rotations I ran into this question at an interview recently. The idea is more to think out loud and work out some reasonable estimates than anything else.
The question is: how many times does an average person's body rotate every day? We don't have to fix a "positive" or "negative" direction. We also don't count small rotations (less than 45 degrees). Imagine walking down a street and then making a 90 degree left. This contributes 90 degrees to our total. If, at the next intersection, we make a 90 degree right turn, this also add 90 degrees to our running count.
I was totally stumped by this question. Usually we are asked to count the number of barbers in Spain or the number of international trains passing through Berlin daily. 
I first tried to split up the rotations we might make into regular and random ones. By regular I mean going to the restroom, getting to work, etc. This was very ineffective because it gives little structure to the exercise. One could easily make the case that I undercounted by a factor of 5 or 10.
Finally I was asked what sort of probability distribution would be good for modelling this. I decided that counting full rotations as discrete units, a Poisson distribution might be approriate. This was met with a frown and after some hints it became obvious that the interviewer wanted to hear the normal distribution. I would love to hear some explanation of this if anyone has an idea.
 A: I would follow your idea of thinking about a typical day.  It is easy to lose them, however.  I probably do two taking a shower, three getting dressed, two more making breakfast, two getting and reading the newspaper, and am not even out of the house yet.  Going on this way, several tens seems like a reasonable guess.  I would be surprised, but not shocked, to average a hundred.
As for the distribution, is it one person's distribution over different days, or the population as a whole?  The one thing it isn't is normal.  As Gerry Myerson implied, there is probably a long positive tail that the normal distribution won't match.  It also doesn't go below zero.  Besides ballerinas, think of stocking clerks.
"Everyone believes in the normal law, the experimenters because they imagine that it is a mathematical theorem, and the mathematicians because they think it is an experimental fact. "— Gabriel Lippmann, conversation with Henri Poincare
A: This link might be useful: http://en.wikipedia.org/wiki/Central_limit_theorem 
