Chapter 8 of 9
Revision Notes
Statistics — Revision Notes
Tamil Nadu Board · Class 9 · Mathematics
Statistics revision notes for Tamil Nadu Board Class 9 Mathematics: 4 topics in quick points. Includes Data and Its Types, Arithmetic Mean and Median.
45 questions25 flashcards4 formulas & key relations5 concepts
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Key Topics to Revise
1
Data and Its Types
- Data means facts, mostly numerical, gathered for a specific purpose.
- Primary Data: First-hand data collected by the investigator himself (e.g., surveys, experiments, interviews).
- Secondary Data: Data taken from an external source already collected by someone else (e.g., government reports, published research).
2
Arithmetic Mean
- Arithmetic Mean (AM) is the most common average, found by dividing the sum of all values by the number of values.
- For Raw Data: Mean = Sum of all observations ÷ Number of observations.
- For Ungrouped Frequency Distribution: Mean = Σfx ÷ Σf, where f is the frequency and x is the value.
3
Median
- Median is the middle value when data is arranged in ascending or descending order — it is a positional average.
- Median is NOT affected by extreme values (very high or very low), unlike the Mean.
- For Raw Data (odd n): Median = value at position ((n+1)/2)th.
4
Mode
- Mode is the value that occurs most frequently in a dataset.
- For raw data: simply identify which value appears the maximum number of times.
- A dataset can have one mode (unimodal), two modes (bimodal), three modes (trimodal), or more (multimodal).
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Full NotesKey Concepts
Data is collected informationRaw data becomes manageable by organizingThe Arithmetic Mean is the mostThe Median is the middle valueThe Mode is the value
Frequently Asked Questions
What are the important topics in Statistics for Tamil Nadu Board Class 9 Mathematics?
Key topics in Statistics include Data and Its Types, Arithmetic Mean, Median, Mode. Study these first, then practise questions on each for Class 9 exams.
How should I revise Statistics for Class 9 exams?
Learn the core ideas first, then work through the 45 practice questions on Statistics. Revise definitions regularly and use flashcards for quick recall before the exam.
Sources & Official References
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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