Mean (x̄)
x̄ = (Σ nᵢ·xᵢ) / N where N = Σnᵢ is total count.
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Lesson overview
This lesson brings together the PDF, study notes and chapter flow so you can revise Statistics without losing the thread.
Mean (x̄)
x̄ = (Σ nᵢ·xᵢ) / N where N = Σnᵢ is total count.
Median
Value that splits the ordered dataset into two equal halves.
Mode
The most frequent value (or class) in the dataset.
Variance (V)
V = (Σ nᵢ(xᵢ − x̄)²) / N = (Σ nᵢxᵢ²)/N − x̄²
Standard deviation (σ)
σ = √V. Smaller σ means data is more concentrated around the mean.
Range
Range = max value − min value.
Relative frequency
fᵢ = nᵢ / N. Sum of frequencies = 1 (or 100%).
Histogram and frequency polygon
Histogram represents counts as bars. Areas are proportional to counts.
Problem-solving method
Identify data, set formulas, solve step by step, then verify sign, unit, and coherence.
Common mistakes
Forgetting domain constraints, mixing equality/equivalence, and losing solutions during transformations.