Identify the statement that correctly defines the proportional model.
a. The proportional model
b. is a probability model in which the frequency of occurrence of an event is proportional to the number of opportunities.
c. is a probability model in which the frequency of occurrence of an event is an increasing function.
d. is a probability model in which the frequency of occurrence of an event is given by an underlying distribution such as the normal or binomial.
e. is a probability model in which the frequency of occurrence of an event is the same for each category.