In graphing a function, which variable is typically treated as the independent variable?

• A. Independent variable
• B. Dependent variable
• C. Response variable
• D. Explanatory variable

Answer: (A)

The key idea is input versus output. In a function, you decide or control the input value first, and the function gives you an output based on that input. The input you set is the independent variable. When you see a function written as y = f(x), the x represents the independent variable because you choose x and then y is determined by the function. On a graph, that input typically sits on the horizontal axis while the output sits on the vertical axis. Terms like response or dependent describe the output, while explanatory is another term for the input in some contexts, but the standard label for the variable you control in a function is the independent variable.