The sum of the absolute frequencies is equal to the total number of data, represented bas $$N$$. 1  Relative frequency: the result of dividing the absolute frequency of a certain value by the total number of data.  The sum of the relative frequencies is equal to $$1$$. We can prove this easily by factorizing $$N$$.
Periodical cicadas emerge from underground every 13 or 17 years, depending upon which brood the cicadas belong to. The year a particular brood emerges often differs from other broods and is also dependent on geography. The periodical cicada, although unrelated, is often mistakenly called a locust.
Why do 17-year cicadas come out more often than every 17 years?long with 17-year cicadas, there are five broods of 13-year cicadas, which are more prevalent in the southeastern part of the U.S. [source: Penn State University ].