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.
Transcript. Why cicadas come out in their prime. I'm Bob Hirshon and this is Science Update. 2004 is the year of Brood Xâa group of cicadas that emerge from the soil every 17 years to molt and mate.Other types come out every 13 years. This prompted one listener from Washington, D.C., to wonder why these insects have such odd-numbered life cycles.We asked biologist Keith Clay of Indiana University.ranscript. Why cicadas come out in their prime. I'm Bob Hirshon and this is Science Update. 2004 is the year of Brood Xâa group of cicadas that emerge from the soil every 17 years to molt and mate.