Normal distribution
Also called: Normal curve, Bell curve · Topic: Geographical Data: Sources, Compilation and Processing · NCERT: Class 12, Ch 2 "Data Processing"
Meaning
A normal distribution is a symmetrical, bell-shaped curve. Most values gather in the middle and thin out evenly towards rare extreme values on both sides. Its mean, median and mode are all equal, and half the values lie above the middle and half below. Some normal curves are tall and narrow (low spread) and others are flat and wide (high spread).
Example
Intelligence and achievement test scores of a large group of students come close to a normal curve. In NCERT's Fig. 2.1, the mean, median and mode all equal 100, with fewer and fewer students towards very low and very high scores.
Don't confuse with
- Skewed distribution: lopsided, with a long tail on one side, so the mean, median and mode separate.