TNPSC Group IV · Bite-size lessons
Data Interpretation
About 7 min · Aptitude and Mental Ability Test · English
Time worked out from the lesson's 465 words at 150 words a minute, plus a minute for each question.
Data Interpretation (DI) is not listed by name in the official TNPSC Group IV syllabus (its percentage and ratio skills are); it tests your ability to read, analyse and draw conclusions from data presented in visual or tabular formats. Unlike pure calculation questions, DI requires you to first understand what the data represents, then perform relatively simple arithmetic to answer questions.
Key ideas
- Tables present exact numerical data in rows and columns. Read row and column headers carefully—they tell you what each number represents.
- Bar Graphs use rectangular bars to compare quantities. Bars can be vertical or horizontal. The height or length represents the value; always check the scale on the axis.
- Pie Charts show parts of a whole as sectors of a circle. The entire circle = 360° = 100%. Each sector's angle or percentage represents its share of the total.
- Line Graphs display trends over time. The slope of the line indicates rate of change—steeper means faster change. Points on the line show exact values at specific times.
- Percentage Change Formula: Change% = [(New – Old) / Old] × 100. A common calculation across all DI types.
Watch out for
- Using wrong base for percentage change → Always use the original/earlier value as the base, not the final value. "Increase from 50 to 60" means base is 50.
- Misreading pie chart angles as percentages → 90° is not 90%. Convert: 90° = (90/360) × 100 = 25%.
- Ignoring scale in bar graphs → If the Y-axis starts at 50 instead of 0, a bar reaching 80 represents 80, not 30. Always check where the axis begins.
Quick reference
- Pie chart: Full circle = 360° = 100%; 1% = 3.6°
- Percentage change: [(Difference) / Original] × 100
- In bar graphs, check Y-axis scale and starting point
- For "ratio of A to B" in pie chart, simply use their angles or percentages directly
- Approximation saves time: 33% ≈ 1/3, 17% ≈ 1/6, 12.5% = 1/8
Check yourself: 3 questions
1. The following table shows the monthly income (in rupees) of five families A, B, C, D and E: Family | Income A | 25000 B | 32000 C | 18000 D | 40000 E | 28000 What is the average monthly income of these five families?
2. A bar graph shows the production of rice (in thousand tonnes) in five states during 2022: Tamil Nadu: 120 Andhra Pradesh: 150 Karnataka: 90 Kerala: 60 Telangana: 180 What is the ratio of rice production in Tamil Nadu to that in Telangana?
3. A pie chart shows the distribution of the annual budget (Rs. 36,00,000) of a company across four departments: Production: 120 degrees Marketing: 90 degrees Research: 60 degrees Administration: 90 degrees What is the budget allocated to the Production department?
This lesson is cut from the topic's note, not rewritten. Fact-checked on 17 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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