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Revision Notes
Index Number — Revision Notes
Gujarat Board · Class 12 · Statistics
Index Number revision notes for Gujarat Board Class 12 Statistics: 4 topics in quick points. Key terms: An index number is, 1 and Index numbers serve as.
12 formulas & key relations5 concepts
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Key Topics to Revise
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1. Definition and Meaning of Index Number
- An index number is the percentage relative change in the value of a variable in the current period compared to its value in the base (reference) period.
- Two methods to measure change: (1) Absolute measure (difference) — NOT always appropriate because it ignores base values; (2) Relative measure (ratio) — APPROPRIATE because it accounts for the base va
- Price relative of an item = (Current year price / Base year price) × 100
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2. Characteristics and Uses of Index Number
- INDEX NUMBER IS UNIT-FREE: Since it is a ratio (relative measure), the units cancel out. This allows comparison of items measured in different units (kg, litre, metre, etc.).
- INDEX NUMBER IS A COMPARATIVE MEASURE: It compares values at two different time periods through ratio.
- INDEX NUMBER IS A SPECIAL AVERAGE: It possesses all characteristics of an average — it summarizes a large dataset into a single representative value.
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3. Base Year — Fixed Base Method and Chain Base Method
- BASE YEAR: A normal, stable year free from unusual events (flood, drought, war, strike, pandemic) used as a reference. Index value of base year = 100.
- FIXED BASE METHOD: One specific stable year is selected as base year for ALL years in the series. All comparisons are made with this single base year.
- CHAIN BASE METHOD: The base year CHANGES for each current year. Each year's index is computed relative to the IMMEDIATELY PRECEDING year.
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4. Conversion Between Fixed Base and Chain Base Index Numbers
- WHEN TO CONVERT: (1) Fixed → Chain Base: When you need to study SHORT-TERM changes from fixed base data. (2) Chain → Fixed Base: When you need to compare a year's value to a SPECIFIC past year from ch
- CONVERSION FORMULA (Fixed → Chain): CBI of current year = (FBI of current year / FBI of previous year) × 100
- CONVERSION FORMULA (Chain → Fixed): FBI of current year = (CBI of current year × FBI of previous year) / 100
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Full NotesKey Concepts
An index number is the percentage1Index numbers serve as economic indicators**Definition**Definition
Frequently Asked Questions
What are the important topics in Index Number for Gujarat Board Class 12 Statistics?
Key topics in Index Number include Definition and Meaning of Index Number, Characteristics and Uses of Index Number, Base Year — Fixed Base Method and Chain Base Method, Conversion Between Fixed Base and Chain Base Index Numbers. Study these first, then practise questions on each for the Gujarat Board Class 12 board exam.
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