Paper 2 · Statistics ⏱ Tested in 5 exam questions since 2024 Lesson 3 of 21

Statistics 3 – Mean, Mode, Median, Range, Interquartile range, Standard Deviation, Percentiles

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You’ll learn

Calculate the mean, mode, median, range and inter-quartile range of a data set
Find σ with the page-33 formula σ = √(Σ(x−μ)²/n) and on your calculator (σx, not sx)
Find percentiles and read quartiles as the 25th, 50th and 75th percentiles
Use population vs sample notation correctly: μ and σ vs x̄ and s

2025 Paper 2 Q4(a)(i) — median of an even-sized list = average of the two middle values. For 12 values, that's t…
2025 Paper 2 Q4(a)(ii) — IQR = Q₃ − Q₁ — find Q₃ as the median of the upper half, subtract Q₁
2025 Paper 2 Q4(b) — mean vs median behaviour under a change to the extremes — the mean is sensitive to all v…
2025 Paper 2 Q4(c) — mean from a frequency table using mid-interval values (MIV): mean = Σ (f · MIV) / Σ f
2024 Paper 2 Q1(a)(i) — mode = the most frequent value

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