What is a bimodal graph?
A bimodal graph illustrates a bimodal distribution, which is itself defined as a continuous probability distribution with two modes. Generally, the graph of this distribution's probability density function will resemble a "two-humped" distribution; that is, rather than the single peak present in a normal distribution or bell curve, the graph will have two peaks.
Bimodal distributions, while perhaps less common than normal distributions, still occur in nature. For example, Hodgkin's Lymphoma is an illness that occurs more often within two specific age groups than among people of other ages; specifically, in young adults 15-35 years old, and in adults past the age of 55.
Thus, for the random variable Z (herein defined as the age of a sufferer of Hodgkin's Lymphoma), the probability density function would possess two modes (or "humps"); one from age 15-35, and one after age 55.