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.
Live Long and Burrow. When the soil warms up enough, cicadas emerge from the ground, where they've been sucking moisture from tree roots for the past 17 years. They'll shed their exoskeletons, attach themselves to branches, mate and lay eggs before dying off in about six weeks.