Detailed notes
Choose arithmetic mean, median or mode to suit the distribution. For paired ungrouped observations, examine scatter diagrams, Karl Pearson correlation and Spearman rank correlation (including ties); correlation describes association and does not establish causation. A simple aggregative price index is Σp₁/Σp₀×100. Interpret CPI, WPI and IIP with their base period and coverage.
Worked interpretation
For prices p₀=(10,20) and p₁=(12,22), the simple aggregative index=(12+22)/(10+20)×100=113.33. It indicates a 13.33% rise in this unweighted two-item basket; it is not a consumer price index for all households.
CBSE-style practice
- For 2,4,4,10: mean=5, median=4, mode=4 and range=8. The high value pulls the mean above the median. For ranks without ties, Spearman ρ=1−6Σd²/[n(n²−1)]; with ties assign average ranks and correlate rank values.
- Draw a labelled graph or table where it clarifies your reasoning.
- State one limitation or assumption.
Quick revision
Define the term precisely, show formula substitutions when relevant, and distinguish a change in the variable from a change in its determinants.