Ecological correlation

{{Short description|Correlation between two variables that are group means}}

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In statistics, an ecological correlation (also spatial correlation) is a correlation between two variables that are group means, in contrast to a correlation between two variables that describe individuals.{{cite journal |first=W. S. |last=Robinson |title=Ecological Correlations and the Behavior of Individuals |journal=American Sociological Review |volume=15 |issue=3 |year=1950 |pages=351-357 |jstor=2087176 }} For example, one might study the correlation between physical activity and weight among sixth-grade children. A study at the individual level might make use of 100 children, then measure both physical activity and weight; the correlation between the two variables would be at the individual level. By contrast, another study might make use of 100 classes of sixth-grade students, then measure the mean physical activity and the mean weight of each of the 100 classes. A correlation between these group means would be an example of an ecological correlation.

Because a correlation describes the measured strength of a relationship, correlations at the group level can be much higher than those at the individual level. Thinking both are equal is an example of ecological fallacy.{{cite book |first=W. Paul |last=Vogt |first2=R. Burke |last2=Johnson |title=Dictionary of Statistics & Methodology: A Nontechnical Guide for the Social Sciences |publisher=Sage |year=2011 |isbn=978-1-4522-3659-9 |page=119 |url=https://books.google.com/books?id=9jHYSm_8Fz4C&pg=PA119 }}