Hi, what kind of graph are you dealing with?
In any case a RATE is a ratio in which (1) there is a unique relationship between the NUMERATOR and the DENOMINATOR; (2) TIME is an intrinsic part of the DENOMINATOR
The incidence (new colds) was 55 per 1000 students during the 3 months of the fall semester
In a RATE, the NUMERATOR is a subset of the DENOMINATOR: the number of students with colds in the 3 months of the fall semester is the numerator and the total number of students at risk for colds is the denominator.
For example: if 870 of 15,975 students had colds in the fall semester, then the RATE of colds is 870colds/15,975 students at risk for colds, or a RATE of .0545 colds/student, or about 55 colds per 1000 students over 3 months.
So once this concept is understood, a graph can be made to reflect the data and the calculation of a rate.
By the way these are real life events where math is vital to answer health and medical questions.
All the best!
