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Statistics in the news (use and abuse)

In early October 2012, the media started running stories about how eating many servings of fruits and vegetables is linked with happiness. The study in question was an observational study of the eating habits of 80,000 Britons and did find that, controlling for other socio-economic variables, high levels of happiness were associated with eating 7-8 servings (2.8oz) of fruits and vegetables per day (Blanchflower, Oswald, & Stewart-Brown, 2012). The study made it clear (in both the abstract and text) that because of its observational nature causality could not be determined:

  • "Reverse causality and problems of confounding remain possible."
  • "This implies that, as in some other parts of the well-being literature, we cannot draw firm inferences about causality."
  • "... with caveats about the lack here of clinching causal evidence..."
  • "... it is sensible to emphasize, first, the need for extreme caution in the interpretation of this study’s findings..."

The authors repeatedly made appropriate statements about the interpretability of the study  and the potential for future controlled studies to determine causality — exactly what one should do. The importance of this work is not diminished because of its observational nature, and serves to fill a gap in the well-being literature and suggest areas for future research.

But then the media happened.

Of course, some sources got the story right:

References

  • Blanchflower, David G., Oswald, Andrew J., and Stewart-Brown, Sarah (2012). Is Psychological Well-Being Linked to the Consumption of Fruit and Vegetables? Social Indicators Research(in press).

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