Statistics for Economics
The Statistics for Economics domain tests how economic data are collected, organised, presented and summarised. The main calculation areas are central tendency and dispersion, with attention to choosing the right measure and class interval.
Core rules and concepts
- Primary data are collected first-hand; secondary data already exist. Census covers every unit; sampling studies a subset.
- A good questionnaire is short, clear, unbiased and logically ordered.
- Classification groups data; tabulation arranges them in rows and columns. Inclusive classes use limits such as 0–10 and 11–20; exclusive classes use 0–10 and 10–20, with the upper limit excluded.
- Mean = sum of observations ÷ number of observations. Median is the middle value in ordered data. Mode is the most frequent value.
- Range = maximum − minimum. Standard deviation measures dispersion around the mean.
Worked example
Daily wages (₹): 100, 120, 120, 150, 200. Mean = 690/5 = ₹138. Ordered data give median = ₹120. Mode = ₹120 because it occurs twice. The mean is pulled upward by ₹200, while the median and mode show the typical wage better. The mean uses every value, so extreme values affect it; the median depends on position.
Traps that cost marks
Do not use the median formula without ordering the data. Do not mix inclusive and exclusive class intervals. Do not say the mean is always best: with outliers or open-ended classes, the median may be more representative. Check units before interpreting dispersion.