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 or Periodical Cicada. Large spring hatches, called broods, emerge in 13 year and 17 year cycles. The 2015 Cicada emergence will have two different broods emerging.Brood IV will arrive in IA,KS,MO,NE,OK, and TX.This brood is a 17 year cycle.icada nymphs suck juices from roots of plants. Egg laying females cause significant damage to trees, bushes and shrubs, during their brief adult stage. They are not harmful to humans. Counter to some rumors, they do not bite, nor do they often land on a human or animal.