National Aeronautics and Space Administration

Shedding a New Light on the Universe

Graphing Activity

by J. Allie Hajian

When making a graph, one variable goes on the X-axis and the other goes on the Y-axis. Is it important which variable goes on which axis?

The answer is, YES!

It is standard that the variable that is "independent" goes on the x-axis and the variable that is "dependent" goes on the y-axis. How do you know which variable is independent and which is dependent? The names "dependent" and "independent" give the necessary clue. Namely, the "independent" variable is the one that can be changed or that varies by itself. The value of the "dependent" variable depends on the value of the independent variable.

For example, if you were graphing rainfall in California vs. time of year, then time of year (in months, for example) would be the independent variable. The amount of rainfall, which depends on the time of year, would be the dependent variable. (There is less rain because it is July; it is not July because there is less rain!)

Exercise

Graph the following, making up your own data. Label the axes.

1. Tree height vs. time (over several years)

2. The speed a car is going vs. the distance it takes to stop completely

3. Cost of house vs. number of rooms in the house

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