Nearly every day, I see a really cool statistic on TV or the interweeb. Everyone gets all excited about losing 312 pounds in four days, curing cancer, or eliminating measles forever. Candy is good for you! Coffee increases your memory! Drink more wine! Eat more Doritos! But if we paid ANY attention to the research methodology, you’d ignore the entire study. Here are a few of the biggest problems I see.
1) Significantly increased memory!!! Yes, when the sample size is large enough or the difference is large enough, anything is significant. So if 5 people in the control group remembered 5 things and 5 people in the test group remembered 8 things, the difference might be statistically significant. Or, if 1000 people in the control remembered 5 things and 1000 people in the test group remembered 5.2 things, the difference might be statistically signficant. Do you trust the results based on 10 people? Do you care about a difference of 0.1 points? I don’t. Get back to me when your sample sizes and effect sizes go beyond pre-test methodology sizes.
2) Cancer rates decreased by 75%!!! Yes, very nice finding. Especially when the cancer rate of the control group was 0.04% and the cancer rate of the test group was 0.01%. That is indeed a 75% decrease but will that massive decline of 0.03 points mean that you stop eating chocolate or start drinking wine? Doubt it. It’s not a meaningful difference when it comes to one single person. Get back to me when the rate decreases by 75% AND the base rate can be measured without any decimal places.
3) Chocolate makes you thin!!!! I’m sure it did. In that one, single study. That has never been replicated. Remember how we compare all our findings against a 5% chance rate? Well, that’s what you just discovered. The 5% chance where the finding occurred randomly. Run the research another 19 times and then get back to me when 19 of them say that chocolate makes you thin.
There are about 423 other cautions to watch out for, but today has been brought to you by the number three.