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.
3,000 known species of cicadas occur worldwide. Periodical cicadas include the large sub-species Magicicada septendecim, who live underground for 13 to 17 years, slowly growing from larvae to adults, then emerge to engage in an ear-splitting, musical mating ritual for four weeks, lay their eggs and die.