Data Representation: Reading Complex Graphs & Tables
The ACT Science section does not primarily test your scientific knowledge—it tests your ability to read and reason from scientific data. Data Representation passages present graphs (line graphs, bar charts, scatter plots) and tables, with questions asking you to read values, identify trends, and interpolate or extrapolate. Interpolation means estimating a value between two known data points; extrapolation means extending a trend beyond the given data range (and is inherently less certain). When a graph has two y-axes (dual-axis), read each curve against its corresponding axis—a common trap is mismatching values. For tables, pay close attention to units: values in mg/L are different from values in g/L by a factor of 1000. The fastest strategy for Data Representation is to skim the passage, read each question, and find the answer directly in the figure without extensive reading. These passages reward students who are confident chart readers. Practice identifying the independent variable (on the x-axis, controlled by the experimenter) and dependent variable (on the y-axis, measured as a result) in every figure.