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Cheat sheet · Class 11 · CBSE · Commerce Economics

Statistics: Measures of Central Tendency cheat sheet

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

CBSE Class 11 · Economics

Cheat sheet

Chapter 5Statistics: Measures of Central Tendency

Mode = 3 Median − 2 Mean (moderately skewed data).

1. Arithmetic Mean

Xˉ=∑XN\bar X = \dfrac{\sum X}{N}Xˉ=∑fX∑f\bar X = \dfrac{\sum fX}{\sum f}
Xˉ=A+∑fd∑f\bar X = A + \dfrac{\sum fd}{\sum f} (assumed mean)
Xˉ=A+∑fd′∑f×h\bar X = A + \dfrac{\sum fd'}{\sum f}\times h (step deviation)

Sum of deviations from the mean is zero.

2. Median

Median=L+N2−cff×h\text{Median} = L + \dfrac{\frac N2 - cf}{f}\times h

Ungrouped: the (N + 1)/2-th item after arranging.

3. Mode

Mode=L+f1−f02f1−f0−f2×h\text{Mode} = L + \dfrac{f_1 - f_0}{2f_1 - f_0 - f_2}\times h

4. Quartiles

Q1Q_1 at N/4N/4, Q3Q_3 at 3N/43N/4 — same formula as median with these positions.

5. Key Points

  • Mean is affected by extreme values.
  • Median for open-ended classes.
  • Mode can be found graphically (histogram).
  • Weighted mean gives importance to items.

Remember: Mean 3 methods | median & mode formulas | quartiles

Statistics: Measures of Central Tendency: questions and notes

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