**Annotation category:**

Chapter 4

Note: |

The rules of probability, described below, will allow you to calculate this value. Briefly, I need to know the fraction of stations that witness such an event each year, the fraction of a year that the 15 minutes following the event represents, and the total time I was in a position to witness such an event (i.e., I was in the subway.) These fractions are then multiplied (see Rule 2 below):

[(10 events/year)x(1/400 stations)]x

[(0.25hr) x (1day/24hr) x (1yr/365d)]

x [(1hr/day) x (365days/yr)]

= 1/4000.

or: *line 1*: events per year per station (chance of being in the right place;*line 2*: fraction of year represented by (death + 15 minutes) (chance of being there at the right time;*line 3*:amount of time I am in subway, (opportunities I had to be in the right place at the right time).