Giving Compass' Take:

• The New Food Economy explores why so many peer-reviewed dietary studies turn out to be either wrong or contradicted by other studies: The problem is in "null hypothesis testing."

• Lay people don't really understand the imperfections of this scientific method, so we extrapolate too much from small sample sizes. The takeaway: Ignore a lot of what's written about in the press and learn what P-value means (P stands for "probability"). If a study has less than a .005 P-value, it's probably not statistically significant.

• Here's why wealthy Americans think they know more about food than they actually do.

Here’s the problem with many of the nutrition studies you’re likely to read about in the press: Like most research, they’re carried out using an incredibly counterintuitive method called “null hypothesis testing.”

It goes like this. First, you start with whatever it is you’d like to prove — say, that drug X cures cancer. But then, instead of trying to prove your hypothesis directly, which is virtually impossible in the real world, you posit its opposite. For example: “I’m trying to prove that any connection between using drug X and curing cancer is just a matter of random chance.” That somewhat confounding non-statement is your null hypothesis.

Then you run your experiment and analyze your numbers. If you’re lucky, you’ll find that there’s not enough evidence to prove no connection between taking drug X and curing cancer. (Confusing, right?) Put another way, you’ve proven that the connection between drug X and cancer cures is not a matter of chance. Therefore, the thinking goes, drug X must cure cancer.

Unless it doesn’t. There are a lot of variables out there that might affect your results: age, weight, sex, smoking, you name it. A good experimental design controls for as many of them as possible. But there’s always the chance (indeed, the likelihood) that more is going on than you know. No one can screen for all possible variables. You don’t get perfection in scientific research.

Read the full article about why 40 percent of peer-reviewed dietary research turns out to be wrong by Patrick Clinton at The New Food Economy.