Short answer: Choose one source with graded sets, solve them under a timer and spend as much time reviewing mistakes as solving. More material rarely helps if you do not review.
What data interpretation asks of you
Data interpretation questions combine reading tables and charts with quick calculation and careful reading of the question. Many errors come from misreading the data rather than from weak maths, so your practice should train reading speed and accuracy together.
Pick graded sets
Look for material that starts with simple tables and charts and then moves to mixed and logic-heavy sets. A mix of formats is useful, including tables, bar and line charts, caselets and arrangement-based sets. If a book has only easy sets, you will need another source later.
Books or online tests
Books let you work at your own pace and mark the page. Online tests add timing pressure. Many students use both in sequence, with books to build the method and tests to practise speed. Our article on quant practice books versus online mocks discusses the same trade-off.
Check the edition and pattern
CAT has changed its pattern over time, so check the exam year the material is written for. If you buy second hand, confirm the edition and make sure the pages are not already filled with answers. Browse second hand books and look at the photos of the inside pages.
A review routine that works
- Time each set before you check answers.
- Mark questions you guessed, even if correct.
- Write down why you went wrong: misreading, calculation or method.
- Redo wrong sets after a week.
How much is enough
Quality beats quantity. A few well-reviewed sets each week are more useful than many rushed ones.
Common mistakes to avoid
A frequent mistake is jumping to the hardest sets because they feel like real preparation. If you cannot read a simple table quickly and accurately, hard sets will only frustrate you. Build the method on easier sets first and increase difficulty in steps.
Another mistake is checking answers without noting why you went wrong. If the cause was a misread label or a unit mix-up, more calculation practice will not fix it. Write down the type of error each time, and you will see patterns within a couple of weeks that tell you what to work on.
Frequently asked questions
Do I need a separate book for data interpretation?
Many CAT books cover it together with logical reasoning. A separate book helps if you want more graded sets, but you can start with one good source.
Is second hand DI practice material fine?
It can be, if the edition is right and the pages are not already solved. Check the inside photos before ordering.
How many DI sets should I solve each week?
There is no fixed number. A few sets that you time and review carefully are more useful than many that you only check for answers.