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.
They typically live in trees, feeding on sap, and laying their eggs in a slit in the bark. Most cicadas are cryptic, singing at night to avoid predators. The periodic cicadas spend most of their lives as underground nymphs, only emerging after 13 or 17 years, most likely to reduce losses by satiating their predators.Cicadas have been featured in literature since the time of Homer's Iliad, and as motifs in art from the Chinese Shang dynasty.ost cicadas go through a life cycle that lasts from two to five years. Some species have much longer life cycles, such as the North American genus, Magicicada, which has a number of distinct  broods  that go through either a 17-year or, in some parts of the world, a 13-year life cycle.