Spurious correlation
Also called: Nonsense correlation, Coincidental correlation · Topic: Economic Data: Census, NSS, Surveys and Statistical Tools · NCERT: Class 11, Ch 6 "Correlation"
Meaning
Spurious correlation is a correlation between two variables that has no real link behind it. It can come about in three ways. It can be pure coincidence. It can come from a third variable that drives both. Or it can come from timing and other factors (confounding) that hide the real effect. It matters because policy built on a false link will fail. Correlation shows only that two things move together. It never proves that one causes the other.
Example
Ice-cream sales and drowning deaths rise together. Ice-cream does not cause drowning: hot weather drives both. In the same way, deaths may rise in villages where more doctors are sent during an epidemic. The doctors did not cause those deaths. The cases were already terminal.
Don't confuse with
- Causation: to show that one thing causes another, you need causal evidence, such as randomised controlled trials (RCTs) or natural experiments. These methods were honoured by the Nobel prizes of 2019 and 2021.
Related concepts
- Measures of central tendency
- Arithmetic mean
- Weighted arithmetic mean
- Median
- Quartiles
- Decile
- Percentiles
- Mode
- Bimodal and multimodal distribution
- Modal class