ACT Science: Mastering Data Interpretation Skills

Title/Caption

The part of a table or graph that gives the experiment context and may state what was measured or under what conditions.

Axes Labels

Labels that identify the variables on a graph; in tables, row and column headers serve the same purpose.

Units

The measurement labels that show scale and meaning, such as mL, L, g, or seconds, and must be checked before comparing values.

Legend/Key

The guide that tells which line, symbol, or color represents each condition or dataset.

Independent Variable

The variable that is changed or controlled in an experiment and is usually placed on the x-axis.

Dependent Variable

The variable that is measured in response to changes in the independent variable and is usually placed on the y-axis.

Two-Way Lookup

A table-reading method in which you match one variable to the correct row and another to the correct column or entry.

Logarithmic Scale

An axis scale where equal spacing represents multiplication by a factor, often 10, rather than equal addition.

Uneven Scale

A graph scale in which tick marks do not represent equal numerical intervals, so spacing must be checked carefully.

Trend

The overall direction or behavior of data as one variable changes, such as increasing, decreasing, or leveling off.

Positive Association

A relationship in which y tends to increase as x increases.

Negative Association

A relationship in which y tends to decrease as x increases.

Plateau

A part of a graph where values stop changing much and level off after rising or falling.

Peak/Optimum

The highest point on a graph, where a variable reaches a maximum before decreasing.

Threshold Behavior

A pattern in which there is little change until a certain x value is reached, followed by rapid change.

Correlation vs. Causation

The distinction between variables changing together and one variable actually causing the change in the other.

Outlier

A data point that does not fit the overall pattern of the rest of the dataset.

Variability

The amount of spread in a dataset; lower variability means the results are more consistent.

Translating Between Data Representations

Changing or matching the same information among tables, graphs, and verbal descriptions without changing the underlying data.

Interpolation

Estimating a value that falls within the range of known data points.

Extrapolation

Estimating a value beyond the measured data range by extending the observed trend.

Slope (Rate of Change)

The change in y divided by the change in x, showing how fast one variable changes per unit of another.

Percent Change

A comparison of a new value to an original value, calculated as ((new - original) / original) × 100%.

Unit Conversion

Changing a measurement into an equivalent unit, such as converting m/min to m/s or L to mL.

Intersection Point

The point where two curves or datasets have the same y-value at the same x-value.