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.
A brood of big, red-eyed cicadas is slowly emerging in the central USA this month after patiently waiting 17 years underground.The noisy critters are popping out across Nebraska, Iowa, Kansas, Missouri, Oklahoma and Texas.here are at least 15 separate cycles, or broods, of periodic cicadas in the USA. Some emerge every 17 years, while others come out every 13 years. Some species show up every summer. This year's group is known as Brood IV, the Kansan Brood..