Detailed Discussion of the Example

Before even answering the specific questions, we first take a look at the graph to get an idea of what information it contains. We see that this is a graph of enrollment figures in five introductory courses at Union University.

As we look more closely, we notice the data groups are not ordered, but are nominal level categories, class name. The frequency data is given in numbers of students enrolled in a course. The scale does begin at zero, and goes to 350. This allows us to make comparisons between bar heights.

Now let's look at the specific questions.

Which course has the most students enrolled in it? Introductory Econ has the most students enrolled. Since the height of each bar is a measure of the number of students enrolled, we simply need to look for the tallest bar. Order the courses by enrollment from lowest to highest. From lowest to highest: Physics, Chem, Psych, Poly Sci, Econ. As with the previous question, we can answer this question by simply looking at the height of the bars, and ordering them from shortest to tallest.	Enrollment in Introductory Courses at Union University
The enrollment in Econ is approximately how many times bigger than the enrollment in Chem? The first thing you should realize is that the answer to this question is the ratio of the number of students enrolled in Econ to the number enrolled in Chem. This ratio is also the ratio of the heights of the two bars:
This ratio could be determined by either reading the number of students for each course off the graph, or just using their relative heights. In this case it looks like the Chem bar is twice as tall as the Econ bar: So enrollment in Econ is 2 times larger than in Chem.
Approximately, how many students were enrolled in the course with the most students?
There are approximately 340 students enrolled in the course with the most students, which is Econ. Estimating numbers off a bar graph is only an approximation. Given the scale of the graph we cannot determine the exact number enrolled. If we look at how tall the Econ bar is, we estimate that 340 students are enrolled.
Approximately how many more students are in Econ than in Physics? There are approximately 200 more students in Econ than in Physics. For this question we want to have a number for the course enrollment for Econ and Physics, then find their difference using subtraction. As in the previous problem, we use bar heights to estimate enrollment.
Estimated Enrollment Econ = 340 Estimated Enrollment Physics = 140 The difference between the two: 340 - 140 = 200 So the difference in enrollment between the two courses is approximately 200 students.

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