Data Interpretation

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Data interpretation gives you a table, bar chart or pie chart and asks several questions from it. No new mathematics is involved — it is percentages, ratios and averages applied to data you are handed. The marks are won on reading accuracy and lost on careless arithmetic.

About the examples on this page. Data interpretation is listed in the official syllabus, but neither the 2022 Constable paper nor the 2022 SI paper actually contained a DI set. The worked examples below are therefore constructed for practice rather than taken from a past paper — unlike every other page in this section. They are marked accordingly.

The Method

1. Read the title, the row and column headings, and the units before anything else.

2. Note whether figures are absolute numbers, percentages, or in thousands / lakhs / crores.

3. Answer each question from the smallest slice of data that settles it.

4. Approximate where the options are far apart; calculate exactly only when they are close.

Units are where marks disappear. A table headed "sales in thousands" turns 45 into 45,000. A pie chart of percentages needs the total before any absolute figure can be found. Check the heading once, at the start, rather than per question.

Formulas You Will Reuse

Asked	Formula
Percentage change	(New − Old) / Old × 100
Percentage of total	Part / Total × 100
Average across a row or column	Sum ÷ number of entries
Pie chart: degrees to value	Value = (degrees / 360) × total
Pie chart: percent to degrees	Degrees = percent × 3.6

Practice Set: Table Interpretation

The table shows the number of candidates (in thousands) who applied for four posts across three recruitment years.

Post	2020	2021	2022
Constable	180	216	270
Sub Inspector	90	108	126
Fire Fighter	60	66	84
Warder	30	30	45

Constructed practice question

By what percentage did Constable applications increase from 2020 to 2022?

Change = 270 − 180 = 90, measured against the 2020 figure.
90 / 180 × 100 = 50%.
The standing trap: dividing by the newer figure gives 33⅓%, which is the wrong base. Percentage change is always measured against the earlier value.

Constructed practice question

In 2021, what percentage of all applications were for Sub Inspector?

Column total for 2021 = 216 + 108 + 66 + 30 = 420 thousand.
108 / 420 × 100 = 25.7% (approximately).
Method: compute a column total once and write it in the margin — DI sets almost always ask two or three questions off the same total.

Constructed practice question

Which post showed the largest percentage growth between 2021 and 2022?

Constable: 54/216 = 25%. Sub Inspector: 18/108 = 16.7%. Fire Fighter: 18/84… careful — against 2021 it is 18/66 = 27.3%. Warder: 15/30 = 50%.
Answer: Warder.
Note: Warder has the smallest absolute rise (15 thousand) but the largest percentage rise, because its base is smallest. Questions are written specifically to separate absolute change from relative change.

Constructed practice question

What is the average number of Fire Fighter applications across the three years?

(60 + 66 + 84) / 3 = 210 / 3 = 70 thousand = 70,000 applications.
Note the units: the table is in thousands, so an answer of "70" is incomplete. Questions often list both 70 and 70,000 among the options.

Do not compute what you were not asked for. A question comparing two rows rarely needs the grand total. In a timed paper, the candidate who totals the whole table before every question runs out of time on an otherwise easy set.

Also see: Percentages · Averages · Ratio & Proportion