Does the study show what caused the result?

A research headline often connects two things: people who used a service improved, a habit was linked with an outcome, or a new method produced better results.

These statements do not all make the same claim. Some describe a pattern. Others say that changing one factor caused a change in another.

To evaluate the headline, examine how the study compared the relevant cases. The central question is what would likely have happened without the proposed cause and how well the study helps answer that question.