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Cheat sheet · JEE Preparation Mathematics

Statistics cheat sheet

The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.

JEE · Mathematics

Cheat sheet

Class 11 · Chapter 13Statistics

Standard deviation = square root of variance.

1. Mean Deviation

MD(xˉ)=∑fi∣xi−xˉ∣NMD(\bar x) = \dfrac{\sum f_i|x_i - \bar x|}{N}

Can be taken about the mean or the median.

2. Variance & SD

σ2=1N∑fi(xi−xˉ)2\sigma^2 = \dfrac1N\sum f_i(x_i - \bar x)^2
σ2=1N∑fixi2−xˉ2\sigma^2 = \dfrac1N\sum f_ix_i^2 - \bar x^2
σ=hNN∑fiyi2−(∑fiyi)2\sigma = \dfrac hN\sqrt{N\sum f_iy_i^2 - \left(\sum f_iy_i\right)^2} (step deviation)

3. Comparing Spread

CV=σxˉ×100CV = \dfrac{\sigma}{\bar x}\times100

Higher CV ⇒ more variability (less consistent).

4. Key Points

  • Range = max − min.
  • Adding a constant: σ unchanged.
  • Multiplying by k: σ multiplied by |k|.
  • Variance is in squared units.

Remember: MD | σ² formulas | CV to compare

Statistics: questions and notes

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