Skewness
Also called: Skewed distribution · Topic: Geographical Data: Sources, Compilation and Processing · NCERT: Class 12, Ch 2 "Data Processing"
Meaning
Skewness means a distribution is lopsided instead of symmetrical, so the mean, median and mode no longer match. In positive skew, the long tail stretches to the right, and mean > median > mode. In negative skew, the long tail stretches to the left, and mean < median < mode. The median always lies between the other two. For skewed data, the median describes the centre better than the mean.
Example
Rainfall in a dry region such as Barmer in western Rajasthan is positively skewed. Most years get little rain, but a few extreme storms bring very heavy falls. These pull the mean above the median. Incomes and landholdings in India are also positively skewed.
Don't confuse with
- Normal distribution: perfectly symmetrical, with mean = median = mode.