Mar 29, 2010

Correlation does not equal causation

I am not a biostatistican, but I can play on on Blogger. Attention science news writers: "Correlation does not equal causation." Can we institute a simple electroshock penalty for those who cite such fraudulent statistics?

Check this out:
"new study finds that older women who use multivitamins may be more likely than non-users to develop breast cancer"
http://www.reuters.com/article/idUSTRE62S4F520100329

Is there any chance of a sampling bias in this study? Any chance at all that the population of elderly women who take multivitamins may be different in any health parameters from the population that finds no need for such supplements? Furthermore, is there any chance that the study subjects taking the vitamins are more likely to be examined more frequently and therefore more likely to have cancer detected?

This reminds me of the brilliant study (cited from the grocery store tabloids by my sister-in-law) that diet soda makes you fat, because a study found that people who drink diet soda were more likely to be overweight than those who do not drink it.


4 comments:

GroovyGeek said...

Everyoone who breathes dies, therefore breathing causes death.

Much of the same can be said about environmental science. I am not a "global warming denier" but I can't help but ask questions about conclusions presented as undeniable truths in the absence of controlled experiments (which are often impossible to do) or any attempt to account for uncontrolled variables.

Bottom line, scientists should do science and refrain from advocating. If you want to advocate quit science and go into politics.

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martha said...

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