I recently received a data set consisting of the number of major hurricanes in the North Atlantic from 1940 to 2007. (Major hurricanes are those that reach Category 3 status or higher at some point during their existence.)

The first step in analyzing any data set is to look at the data. This means plotting the data in some meaningful format. With data that form a time series, the simplest and best format will be the running record where the data are plotted in time order. The running record for the number of major hurricanes is shown in figure 1.

The first question of data analysis must always be whether the data are homogeneous. If the data are, then we can use them with the various computations commonly taught in statistics classes. However, if the data aren’t homogeneous, then the question becomes, “Why or when did the changes occur?”

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