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Show physical reality. They predict probable consequences but do not assign causes. Second, both tables are based on the assumption that occurrences of the event in questibn ( in this case major avalanches) are random and independent. This means that the encounter probability does not change because the event occurs. This is another way of stating the gambler's maxim: " The laws of chance have no memory." Table 1 is calculated on the assumption that the events occur only at integers on the time scale. This may seem an arbitrary and impractical restriction, but in the case of avalanche hazard it has some useful applications. If most avalanches of a damaging size are known to occur at a given site in, say, January, then such events will fall close to the time scale integers if the convenient time unit of a year is chosen. Table 2 removes this restriction, allowing the events to occur at any point on the time scale. The following mathematical restrictions, however, have5; been observed in calculating Table 2: The process is stationary, possesses independent increments, and has a time- independent average. Two or more events cannot occur simultaneously. Allowing the events to occur at any point on the time scale gives a more realistic flexibility to the calculations, but does raise another problem when dealing with avalanches in time units of years. Avalanches do not occur at any point on such a time scale; they occur only in the winter. This difficulty may be circumvented if the chosen time unit is winter months for both the return interval and the estimated life. The estimate of encounter probability is then based on a continuous time scale made up of years consisting of those four or five winter months when avalanche damage is possible. The balance of each year |