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.
Most cicadas are cryptic, singing at night to avoid predators. The periodic cicadas spend most of their lives as underground nymphs, emerging only after 13 or 17 years, which may reduce losses by starving their predators and eventually emerging in huge numbers which overwhelm and satiate any remaining predators.