Finding the probability of a rare real world event

Abstract

One of the nicer things about growing older is that you tend to find a great deal of pleasure in the little rituals of life. Things like morning coffee or tea, a warm bath, or a glass of good wine at the end of the day. There are some rituals, however, that are not at all enjoyable. Take, for example, the monthly ritual of paying bills. I still do this by cheque, so I need to make sure my bank account balance is sufficient to pay the cheque, write the cheque, and subtract the cheque amount from the account balance. Now there is a little pleasure when one actually adds money to the account balance, but the one time that gives me more than a modicum of joy is when the pence portion of the account balance comes out to be exactly zero. This happens very rarely and unpredictably. As a statistician I became intrigued with trying to find the probability of this event occurring. I did an extensive literature search both in traditional hard copy journals and also online, but I could find no reference to this problem.