Lesson 27 — Activity 2: Reading a Graph

Getting Ready

In the last activity, you learned what independent and dependent events were. In this activity, you are going to learn about independent and dependent variables in relation to a graph.

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Independent and dependent variables are part of graphs. The independent, or manipulated variable, goes on the x-axis. The x-axis is at the bottom of the graph. The reason we call this the manipulated variable is because it is the variable that can change. It is also the variable that affects the outcome.

The dependent variable goes on the y-axis. The y-axis is the vertical side of the graph. It is affected by the independent variable.

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Let's look at a graph comparing height and weight. This graph will deal with height in inches and weight in pounds.

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Look at the graph. As you move along the x-axis (height), the weight increases. Therefore, the weight is dependent upon the height.

Find 40 on the x-axis. Go straight up until you reach the line on the graph. Then read across to the y-axis. The y-axis is approximately 85. This means that when someone is 40 inches tall, they weigh about 85 pounds. How much does someone weigh when they are 60 inches tall? Using the same steps that you did for 40 inches, you can see the weight is approximately 130 pounds when someone is 60 inches high.

Another graph is time studied versus a mark on a test.

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As you can see, the more time you study for a test, the better you will do! As you manipulate the number of hours that you study for a test, the mark on the test increases. The mark depends on the time spent studying.

For this example, 4 hours of studying means you receive a mark of 60% on the test, while 7 hours of studying means you will receive a mark of 90% on the test.


Try this!

Complete this Self Check on independent versus dependent variables on a graph.

Use the graphs to answer the questions below each graph.