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.
The growing cicada then spends the next 13 to 17 years underground as a nymph. Juvenile cicadas live at depths of 30 centimetres or more and subsist on the juices of plant roots until the final year. When the soil temperature reaches about 18 degrees Celsius, they burrow their way to the surface.