## Basic Math and Pre-Algebra

**PART 4. The State of the World**

**CHAPTER 19. Graphs**

**Histogram**

There’s another type of graph that, at first glance, may look a lot like a bar graph, but there are some key differences. The graph is called a histogram. It does use bars, but instead of representing different categories, this graph tells you how often a particular number or measurement showed up in the data. A histogram is an example of a frequency graph. It tells you how often, how frequently, a particular value occurs.

If you surveyed a group of people and asked how many pets they owned, you would likely get answers ranging from 0 to perhaps 5 or 6. It’s also likely that there will be more than one person giving each of those answers. You could draw a histogram to show how many people gave each answer.

Notice that in the histogram the bars are touching, but in the bar graph there was space between them. That’s because in a bar graph the categories on the horizontal axis are separate from one another. In the histogram, the horizontal axis has all the possible answers in numerical order, and every number on that axis is counted in one of the bars. Each bar picks up just where the last one left off, and no value on the horizontal axis is left out.