Which element on a standard research graph is not itself a variable?

• A. The dependent variable
• B. The independent variable
• C. The data points
• D. The trend line

Answer: (D)

Variables are the quantities you study: the independent variable is what you change, and the dependent variable is what you measure. The data points are the actual measurements plotted from those variables—observations that reflect those variables but are not themselves variables. The trend line, on the other hand, is a calculated summary that shows the overall pattern in the data; it’s a model, not a quantity you measure or control. Because it isn’t something you collect as a value or manipulate, it isn’t a variable. So the trend line is the element that isn’t a variable.