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Research Methods: Correlation and Causation

Discuss the differences between the concepts of correlation and causality and why it is critically important to make sure that the differences are understood.

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Two specific examples of confusing correlation and causality come to mind that had significant ramifications.

The first is confusion in the 1960s regarding the cause of the observed increased incidence of lung cancer. Prior to the 1900s, lung cancer was not a common condition, but the incidence began increasing in the 1940s, but more so in the 1950s. A prime consideration was the large increase in paving that occurred in the same time period. After all, petroleum products, e.g., asphalt, are noxious to breath in, and there was concern that the volatile components of paving materials might be causative. This was reinforced by the observation that a correlation existed between the miles of road paved and the incidence of lung cancer per year. The competing hypothesis was that smoking incidence had increased ...

Solution Summary

Correlation is a mathematical relationship between two or more processes. Such correlations may be demonstrated between conditions that are unrelated in any other way. Cause and effect also show a mathematical relationship, but the difference is that the cause is very related to the effect. Mistaking correlation for causation may lead to fruitless investigations, treatments, and litigation.