## 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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