Data Interpretation (DI) questions account for roughly 6 of your 27 Quant questions, grouped into sets of 2-5 questions that all reference the same data display. You read one chart, then answer multiple questions from it. The format rewards students who know how to read a data display before touching the questions.
Most people lose points on DI not because they cannot do the math, but because they misread the chart. They pull the wrong value, calculate on the wrong base, or miss a unit label. The math itself is rarely harder than middle school arithmetic. The challenge is accurate extraction under time pressure.
What DI Looks Like
Each DI set gives you one data display shared across all questions in that set. The display could be a bar chart, line graph, pie chart, table, scatterplot, or boxplot. You get 2-5 questions all drawing from that single source.
This structure means you should spend 60-90 seconds reading and orienting to the data display before you touch any question. That upfront investment pays off on every subsequent question in the set. Students who skip straight to question 1 end up re-reading the chart for every question and missing details they would have caught on a careful first read.
The Charts Are Drawn to Scale
This is one of the most important distinctions on the GRE Quant section: DI charts and data displays are drawn to scale. You can trust what you see visually.
This is the opposite of geometry figures in the Quant section, which are explicitly not drawn to scale. With a QC or PS geometry problem, you cannot assume two angles are equal because they look equal. With a DI chart, you can. A bar that looks twice as tall as another bar is approximately twice as tall. A pie slice that looks like 25% of the circle is approximately 25%.
This does not mean you should eyeball values instead of reading them precisely when gridlines are available. But it does mean that visual proportion is useful for sanity-checking your answers and for estimation when exact values are not readable.
Chart Types and How to Approach Each
Bar charts are the most common. Read the axis labels before anything else. Check whether the y-axis starts at zero or uses a broken axis that visually exaggerates differences. Read the legend if bars are grouped or stacked. For grouped bars, be clear on which bar you are reading before you write down a value.
Line graphs show change over time. The slope between two points tells you the direction of change, but you need to calculate the actual percent change using the values, not the visual steepness of the line. Two segments that look equally steep on different parts of the graph may represent very different percent changes if the starting values are different.
Pie charts show parts of a whole. The whole is always 100%, which is usually stated as some total number (total revenue, total employees, total sales). The most common trap: a slice represents a percentage of the whole, but you need an actual count. Make sure you multiply the percentage by the correct total.
Tables give you exact values. They are the easiest to read accurately and the hardest to scan quickly. On a table, identify the rows and columns before you look at any question. Understand what each axis represents. When a question asks about a specific cell, find the row first, then move across to the correct column. Do not scan around hoping to spot the number.
Scatterplots show the relationship between two variables across individual data points. Questions typically ask you to identify the point closest to a given description, estimate a count of points meeting a condition, or read the approximate value of a specific point.
Boxplots show distribution: minimum, first quartile (Q1), median (Q2), third quartile (Q3), and maximum. The box spans Q1 to Q3. The line inside the box is the median. The whiskers extend to the min and max. Questions typically ask you to compare medians, compare ranges, or identify which dataset has greater spread. The interquartile range (IQR) is Q3 minus Q1.
Trap 1: Percent Change on the Wrong Base
This is the single most common DI error. Percent change is always calculated against the original value, not the new value.
Percent change = (New - Old) / Old x 100
If sales went from 200 to 300, the percent change is (300 - 200) / 200 = 50%.
The trap version: the question shows you both values but expects you to use the ending value as the base. Answer choices are designed so that if you divide by the new value instead of the old value, you get a plausible-looking number that appears in the answer list.
Any time a DI question asks "by what percent did X increase" or "what was the percent change from year A to year B," slow down and confirm: which value is the original? That value goes in the denominator.
Trap 2: "In Thousands" and "In Millions" Axis Labels
Charts frequently label their axes with a unit multiplier. The axis might read "Revenue (in millions of dollars)" with a tick at 2, meaning 2,000,000, not 2.
This trap is sneaky because calculations within the same chart still work fine, since both values carry the same multiplier. The error shows up when a question asks you to combine data from the chart with an external number, or when an answer choice is stated in raw units rather than scaled units.
Before you read any values off the chart, note the unit. Write it down. If the axis says "in thousands," every number you extract needs a mental note that it represents a value 1,000 times larger than the label.
Trap 3: Broken Y-Axis
A broken y-axis starts above zero, often marked with a small diagonal break in the axis line near the bottom. The practical effect: differences between bars or lines look much larger than they actually are.
A bar at 42 and a bar at 40 on a broken axis starting at 38 will look like one bar is 100% taller than the other, when the actual difference is about 5%.
When you see bars or lines that look dramatically different from each other, glance at the bottom of the y-axis. If it does not start at zero, recalculate any percent differences using the actual axis values, not the visual heights.
Pacing DI Sets
Target: read the data display in 60-90 seconds, then 60-90 seconds per question.
For a 3-question DI set: roughly 3.5-4.5 minutes total. For a 5-question set: 5.5-6.5 minutes total. DI sets are slower per question than standalone PS questions because of the chart-reading overhead, but the payoff is that questions within the set share a single chart that you only decode once.
Practical approach:
- Read the title and all axis/column labels first.
- Note units and any multipliers.
- Scan the overall shape of the data: what is high, what is low, what is the time range, what categories exist.
- Then read question 1.
Do not skim the chart and immediately dive into calculations. Students who skip step 3 frequently calculate the right number from the wrong category or the wrong year.
When Estimation Is Enough
DI questions often have answer choices spread far enough apart that you do not need a precise calculation. If the answer choices are 12%, 18%, 24%, 34%, and 48%, and your estimate gives you roughly 17-19%, you can confidently choose 18% without working out the division to three decimal places.
Before doing precise arithmetic, look at the answer choices. If they are clustered tightly together (e.g., 18.2%, 18.8%, 19.4%), you need to be precise. If they are spread widely, estimate first and refine only if your estimate lands between two choices.
Reading Multiple Data Displays
Some DI sets include two linked displays, such as a bar chart and a table describing the same dataset from different angles. The questions may require you to combine values from both.
When this happens, identify the linking variable first. Usually there is a shared category (same company, same year, same product) that appears in both displays. Make sure you are drawing the correct values from the correct display for each quantity the question asks about.
Practicing DI Effectively
DI errors are almost always traceable to a specific misread, not a knowledge gap. That makes error review more actionable for DI than for most question types.
After each DI practice set, go back and identify exactly where the error occurred: Was it a wrong value extracted from the chart? Wrong base for percent change? Missed unit multiplier? Each of those is a distinct habit to fix.
The GRE practice builder lets you filter by question type and includes DI sets across all chart types. Working through DI sets in timed conditions, then reviewing the precise source of each error, is the fastest way to stabilize your DI accuracy.
The math ceiling for DI is low. You rarely need anything beyond arithmetic and percent calculations. The actual skill being tested is systematic, accurate reading under time pressure. Build a consistent chart-reading protocol, apply it on every set, and your DI accuracy will stabilize quickly.