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Data Interpretation
and Graphs

Master the art of reading bar charts, pie charts, line graphs, and tables to solve GRE Quantitative questions with speed and accuracy.

GRE Quantitative

What Is Data Interpretation?

Data Interpretation (DI) questions present information in visual formats: charts, graphs, and tables. Your task is to extract specific values, compute relationships, and draw conclusions from the data provided.

Extract
Read precise values from axes, bars, slices, or cells
Compute
Calculate percentages, ratios, differences, and averages
Conclude
Identify trends, compare categories, and make inferences

The Four Graph Types You Must Know

Bar Chart
Compares discrete categories. Heights or lengths represent values.
Line Graph
Shows trends over time. Slope indicates rate of change.
Pie Chart
Shows parts of a whole. A slice's angle is its percentage of \(360^\circ\).
Table
Precise numerical data in rows and columns. Exact values, no estimation.

Anatomy of a Bar Chart

0 20 40 60 80 Revenue ($M) 40 60 80 70 Q1 Q2 Q3 Q4 Peak Quarter

Essential Formulas for DI

1
Percentage: \(\text{Percentage} = \dfrac{\text{Part}}{\text{Whole}} \times 100\)
2
Percent Change: \(\text{Change} = \dfrac{\text{New} - \text{Old}}{\text{Old}} \times 100\%\)
3
Weighted Average: \(\bar{x} = \dfrac{\sum w_i \cdot x_i}{\sum w_i}\)
4
Pie Slice Angle: \(\text{Angle} = \dfrac{\text{Category Value}}{\text{Total}} \times 360^\circ\)

Bar vs. Line vs. Pie

Bar Chart Line Graph Pie Chart
Best For Comparing categories Trends over time Parts of a whole
Key Skill Estimate heights Identify slope Compute percentages
Precision Moderate (read axis) Low (interpolate) Low (estimate slices)
GRE Trap Stacked vs. grouped \(\text{Flat} \neq 0\) \(\text{Slice} \neq \text{raw count}\)

How to Approach DI Problems

1
Read the title and axis labels first. Know what the graph is measuring before looking at any data point.
2
Check the units and scale. Is the y-axis in thousands? Millions? Are values percentages or absolute numbers?
3
Read the question carefully. Are they asking for a value, a difference, a percentage, or a ratio?
4
Extract only the numbers you need. Resist computing everything: focus on what the question asks.
5
Use estimation liberally. GRE answer choices are spread apart: precise calculation is rarely necessary.

Example 1: Reading a Bar Chart

0 50 100 150 200 Students 100 150 200 125 Math English Science History Subject Enrollment

Example 2: Pie Chart Calculations

\(35\%\)
\(25\%\)
\(20\%\)
\(20\%\)
 Rent: \(35\%\) Food: \(25\%\) Transport: \(20\%\) Other: \(20\%\) Monthly Budget: \(\$4,000\)

Example 3: Line Graph and Percent Change

0 100 200 300 400 Sales ($K) 2019 2020 2021 2022 150 200 350 300

Working with Tables

Region 2021 Sales 2022 Sales Change
North $120K $150K \(+25\%\)
South $200K $180K \(-10\%\)
East $80K $100K \(+25\%\)
West $160K $200K \(+25\%\)

The Power of Estimation

GRE answer choices for DI questions are typically spread far apart. You rarely need exact arithmetic. Instead, use rounding and approximation to save valuable time.

Round first
\(198 \approx 200\), \(4{,}850 \approx 5{,}000\). Round to friendly numbers before computing.
Benchmark fractions
\(\frac{1}{3} \approx 33\%\), \(\frac{1}{8} = 12.5\%\). Use known fractions to estimate quickly.

Stacked vs. Grouped Bar Charts

Stacked 0 50 100 150 60 40 80 50 A B Grouped 0 50 100 A B Category 1 Category 2

Handling Multi-Display Data Sets

GRE DI questions often present two or three displays together: a pie chart showing percentage breakdowns alongside a table with totals. You must cross-reference both to answer.

1
Identify the link. Find the shared variable between displays (e.g., "total revenue" appears in the table while percentage shares are in the pie).
2
Convert between formats. If the pie shows \(30\%\) and the table says the total is \(\$500\text{K}\), then the value is \(0.30 \times \$500\text{K} = \$150\text{K}\).
3
Watch the years. One display may cover 2020 while another covers 2021. Confirm you are using matching time periods.

Common Mistakes to Avoid

✕ Ignoring Units
Reading "\(\$200\)" from a graph labeled "in thousands" means the actual value is \(\$200{,}000\).
✕ Wrong Base for Percent Change
Percent change uses the original value as the base, not the new value.
✕ Stacked Bar Misread
Reading a stacked bar segment from the baseline instead of from the top of the segment below.
✕ Pie Chart \(\neq\) Count
A larger pie slice means a larger share, not necessarily a larger absolute number. Context matters.

DI Cheat Sheet

Skill What to Do Watch Out For
Read values Use gridlines, not eyeball Axis starts at non-zero
Percent change \(\frac{\text{New}-\text{Old}}{\text{Old}}\times100\) Wrong base value
Pie charts Multiply % by total \(\% \neq \text{absolute count}\)
Tables Extract exact values Mismatched units/years
Estimation Round, then compute Over-computing

Question 1 of 5

A bar chart shows Company X's revenue was \(\$300\text{K}\) in 2021 and \(\$360\text{K}\) in 2022. What is the approximate percent increase?

Question 2 of 5

A pie chart shows that "Marketing" accounts for \(18\%\) of a company's total budget of \(\$500{,}000\). How much is spent on Marketing?

Question 3 of 5

In a stacked bar chart, the bottom segment for Year 2020 goes from \(0\) to \(120\) and the top segment goes from \(120\) to \(200\). What is the value of the top segment alone?

Question 4 of 5

A line graph shows values of \(400, 500, 450, 600\) for years 2019 through 2022. Between which consecutive pair of years was the percent increase the greatest?

Question 5 of 5

Which region had the greatest absolute increase in sales from 2021 to 2022?