Graphing

We've collected and averaged our measurements, but what now?

We don't just want a list of numbers. We want a way to see the data.

Graphs help us make sense of results in a clear visual way.

So here's our situation. We measured the average distance a racer traveled when released from four different heights. Which type of graph would work best to show this data? A line graph, a bar graph, or a pie chart.

Let's review each type of graph and how they are used.

A line graph connects data points with lines. It shows how something changes over time. For example, a line graph might show how a plant grows over the course of several days.

A bar graph uses bars to represent categories. Each bar shows the value for a specific category. Bar graphs are great for comparing. Like in this example that shows how students in a class get to school.

A pie chart shows parts of a whole. Each slice represents a percentage or a part of the total. For example, a pie chart might show what fraction of your day you spend sleeping, playing, at school, or doing something else.

So, which one fits our data best? We want to compare four categories. The distance a racer travels when released from four different heights. We are comparing those heights. That makes a bar graph the best choice.

So let's talk about how to set up a bar graph. Every graph needs a title and labels to explain what it's showing. I'm going to title this graph, racer distances at different heights.

The x axis, that horizontal line along the bottom, will show the categories. In this case, the four different heights. Ground, level one, level two, and level three.

The y axis, the vertical line, shows the distances the racer traveled in centimeters. Each line or tick mark must represent an interval that fits the range of our data.

Think about it as a number line that begins at zero and must reach at least one hundred eight, our largest data point. If I count by twos, that won't work. So I need to try something bigger, like counting by tens.

Once we set the scale and label all of the tick marks, we can draw one bar for each category. The length of the bar represents the racer's average distance from that release height.

When all four bars are drawn, we can easily compare them side by side.

So, bar graphs are powerful tools for comparing categories. For our racer data, they make it easy to see how the height affects the distance, all at a quick glance.