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.
Other names: Cicadas are also called 17 year Locust, Cicada insects and Periodical Cicada. Large spring hatches, called broods, emerge in 13 year and 17 year cycles. The 2017 Cicada emergence will have one brood emerging. Brood VI will arrive in Georgia, North Carolina and South Carolina. This brood is a 17 year cycle.