The concept of variables crops up in almost every math or science class, and understanding the difference between a dependent and independent variable provides the basis for understanding more complex material.

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## Independent vs. Dependent Variables

In science, the independent variable is the one the scientist changes on purpose while the dependent variable is not changed or manipulated, only measured. For example, a scientist might water a plant different amounts of water at different times (this would be the independent variable) and then measure how much the plant grows with each amount of water (the dependent variable)

## Input vs. Output

In Algebra, the dependent variable is the "y" variable because it represents the number that comes out of a equation depending on the input variable, the "x." If two other letters are used, the one that comes first alphabetically is considered the independent variable and the later one is considered the dependent.

## Graphing

On a graph, the dependent variable is graphed on the side (what would be the "y" axis in math) while the independent variable is graphed on the bottom (the "x" axis in math). Both variables are labelled on the graph and described using the units with which they were measured--eg. plant height in feet.