Summary

The examples just given illustrate the basic idea of probability: it is a way of expressing ideas or theories about the relative frequency of an uncertain event. The illustrations involved uncertainty about whether a person we encounter would be left-handed, or would self-identify as Asian-American. The same ideas apply to uncertain events that refer to weather, climate, and various kinds of hazards. For example, by using mathematical analysis combined with practical experience, meteorologists can usually estimate the probability of rain tomorrow, in a certain city; climatologists may be able to estimate the probability of very little rainfall in a particular region next rainy season; and seismologists may estimate the probability of a major earthquake in a certain region within the next 30 years.