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Graphs & Data Interpretation for the PSAT/NMSQT: Complete Study Guide + Free Practice Problems
Everything the PSAT/NMSQT tests about reading graphs and data in one place: bar graphs and histograms, line graphs and scatterplots, tables and two-way tables, pie charts, and reading scales and axes carefully — with worked examples and a free practice quiz.
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Free · No signupGraphs & Data Interpretation
Bar graphs, line graphs, scatterplots, tables, and pie charts.
What does the PSAT test with graphs?
Data interpretation questions ask you to read information directly from a chart, graph, or table — often without requiring much calculation at all. The real skill being tested is careful, accurate reading: identifying the right row, column, bar, or point before doing any arithmetic.
Before answering, always read the title, axis labels, and units of a graph or table first. Many wrong answers come from misreading what's being measured, not from a math mistake.
Bar graphs & histograms
| Chart | What it shows |
|---|---|
| Bar graph | Compares values across separate, distinct categories |
| Histogram | Shows frequency of numeric data grouped into continuous intervals |
A bar graph shows monthly sales: January = 40, February = 55, March = 30. What is the total sales across these three months?
In a histogram, each bar represents a range of values (like "10–19"), not a single value. Always check what the width of each bar represents before reading frequencies.
Line graphs & scatterplots
A line graph connects data points to show a trend, often over time. A scatterplot shows individual points without connecting them, used to explore the relationship between two variables.
A line graph shows a company's revenue was $200,000 in Year 1 and $350,000 in Year 4. What was the average yearly increase?
Tables & two-way tables
A two-way table organizes data by two categories at once. Most table-reading questions require you to correctly identify whether you need a specific cell, a full row total, or a full column total.
| Prefers Bus | Prefers Car | Total | |
|---|---|---|---|
| Grade 11 | 35 | 45 | 80 |
| Grade 12 | 25 | 55 | 80 |
| Total | 60 | 100 | 160 |
Using the table above, what fraction of Grade 12 students prefer the bus?
Pie charts
A pie chart (circle graph) shows how a whole is divided into parts, usually as percentages that add up to 100%.
A pie chart shows a household budget of $4,000, with 15% spent on transportation. How much is spent on transportation?
All the percentages (or angle measures) in a pie chart must add up to 100% (or 360°). If a question gives you all but one slice, subtract from the total to find the missing piece.
Reading scales & axes carefully
- Check the axis units: confirm whether values are in ones, thousands, or another scale before reading a value off a graph.
- Check for a broken or non-zero axis: some graphs start at a value other than zero, which can visually exaggerate differences between bars.
- Check gridline spacing: not every gridline represents the same increment — confirm the value each line represents before estimating a point's position.
A graph with a y-axis that doesn't start at zero can make small differences look dramatic. Always check the actual numeric values represented, not just the visual height of the bars or points.
Common PSAT traps
- Misreading axis units or scale: double-check whether values are labeled in single units, hundreds, or thousands.
- Confusing row and column totals in a table: read the table headers carefully before dividing.
- Estimating from a visually misleading graph: rely on labeled values, not the apparent height or size of a bar or slice.
- Forgetting percentages in a pie chart must sum to 100%: use this fact to find any missing slice.
Test day strategy for graphs & data interpretation
| Question signal | Fastest approach |
|---|---|
| Any graph or chart given | Read the title, axis labels, and units before doing any calculation |
| "Total" or "sum" across categories | Add the relevant bar or table values directly |
| Rate of change over time | Divide the total change by the elapsed time interval |
| Two-way table question | Identify whether you need a row, column, or single cell before dividing |
| Pie chart with a missing slice | Subtract the known percentages from 100% |
Now put it to work
One comprehensive quiz covering the full topic — bar graphs, line graphs, scatterplots, tables, and pie charts.
Graphs & Data Interpretation
Bar graphs, line graphs, scatterplots, tables, and pie charts.