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Statistics

Tamil Nadu Board · Class 9 · Mathematics

Quick revision notes for Statistics — Tamil Nadu Board Class 9 Mathematics. Key concepts, formulas, and definitions for last-minute revision.

45 questions25 flashcards5 concepts

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An illustration comparing raw (ungrouped) data, arrayed data (sorted), and tabulated data (organized in a basic table with categories and totals).
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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 Notes

Key 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 Statistics Chapter Overview Mind Map, Statistics Chapter - Complete Concept Map, Mind map showing the types of data collection methods and their categories. These are the concepts Tamil Nadu Board Class 9 examiners draw on most — study them first, then practise related questions.
How to score full marks in Statistics — Tamil Nadu Board Class 9 Mathematics?
Understand the core concepts first, then work through the 45 practice questions available for this chapter. Revise formulas and 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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All 9 chapters — Tamil Nadu Board Class 9 Mathematics Revision Notes

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