Statistics — Syllabus
Tamil Nadu Board · Class 9 · Mathematics
What Statistics covers in Tamil Nadu Board Class 9 Mathematics: 4 topics, for the 2026-27 session. Topics include Data and Its Types, Arithmetic Mean.
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Topics in Statistics
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).
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.
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.
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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