Class 10 Maths Chapter 13 Statistics Revision Notes

Class 10 Maths Chapter 13 – Statistics: Quick Revision Notes

• Class mark xᵢ = (Upper limit + Lower limit)/2
• Mean (Direct): x̄ = Σfᵢxᵢ/Σfᵢ
• Mean (Assumed Mean): x̄ = a + Σfᵢdᵢ/Σfᵢ, dᵢ=xᵢ-a — use for unequal class widths
• Mean (Step-Deviation): x̄ = a + (Σfᵢuᵢ/Σfᵢ)×h, uᵢ=(xᵢ-a)/h — use for equal widths, large numbers
• All three mean methods always give the same numeric answer
• Inclusive/gapped classes must be converted to continuous classes first (adjust limits by half the gap)
• Mode = l + [(f₁-f₀)/(2f₁-f₀-f₂)] × h — modal class = class with highest frequency
• Median = l + [(n/2-cf)/f] × h — median class = first class whose cf ≥ n/2, found from a cumulative frequency table
• “Less than” cumulative tables must be converted to individual class frequencies before use
• Empirical relationship: Mode = 3 Median − 2 Mean (equivalently 3 Median = Mode + 2 Mean)
• Ogive: less-than ogive rises (upper limits vs cf); more-than ogive falls (lower limits vs cf); their intersection’s x-coordinate gives the median graphically
• Common trap: modal class = highest frequency, NOT highest cumulative frequency

More on This Chapter

• NCERT Solutions – Chapter 13
• Extra Questions (HOTS) – Chapter 13
• Revision Notes – Chapter 13
• Class 10 Maths Book (Catalog Page)

Written by Satish

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