IB Psychology Graph and Chart Interpretation

Vocabulary terms and definitions for interpreting various graph types and data features within IB Psychology foundational concepts.

Independent Variable (IV)

The variable being manipulated or measured — always on the horizontal axis (x-axis).

Dependent Variable (DV)

The variable being measured as a result — always on the vertical axis (y-axis).

Line Graphs

Visuals used to show changes in a variable over time or across conditions.

Line Graphs Key Features to Identify

• Trend direction (increasing, decreasing, stable).

• Rate of change (steep vs. gradual).

• Peaks and troughs (highest/lowest points).

• Intersection points (where lines cross, indicating comparison).

Trend Direction

A feature of line graphs used to identify if data is increasing, decreasing, or stable.

Bar Charts / Histograms

Visuals showing comparisons between different groups or categories.

Bar Charts / Histograms Key Features to Identify

• Height differences (which group scored highest/lowest).

• Patterns across groups.

• Variability between bars.

• Example application: "How do memory scores differ across age groups?"

Scatter Plots

Visuals used to show the relationship or correlation between two variables through patterns of dots.

Scatter Plots Key Features to Identify

• Pattern of dots (positive correlation = upward trend; negative correlation = downward trend; no correlation = random).

• Strength of correlation (tight cluster vs. spread out).

• Outliers (points far from the trend).

Positive Correlation

An upward trend in a scatter plot indicating a direct relationship between variables.

Negative Correlation

A downward trend in a scatter plot indicating an inverse relationship between variables.

Outliers

Data points that are far from the trend or beyond the whiskers in a box plot.

Box Plots (Whisker Plots)

Visuals showing the distribution and spread of data, including median, quartiles, and range.

Median

The middle line in the box of a box plot representing the central value of the data set.

Interquartile Range

The box size in a box plot which represents the spread of the middle data.

Pie Charts

Visuals displaying proportions or percentages of a whole through slice sizes.

Area Graphs

Visuals showing cumulative change over time or stacked categories.

Longitudinal Studies (Graphing)

Typically use line graphs to demonstrate development or effects over time, such as cognitive development with age.

Correlational Studies (Graphing)

Typically use scatter plots to examine links between variables, such as stress vs. memory performance.

Scale

The numerical ranges found on the axes of a graph.

Trough

The lowest point on a line graph.

Peak

The highest point on a line graph.