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Justification For Self-Experimentation and My Belief that N=1 Results Will Generalize

Posted Dec 16 2011 12:00am

At the Quantified Self blog, in response to a video of me talking about QS and the Ancestral Health Symposium (paleo), someone named Colin made :

Very interesting talk. I am just curious how someone can claim a study conducted with a sample size of one is “100 times better” than someone else’s study. I do not know anything about the other study mentioned, but I do know that a study based on n=1 cannot be considered scientific proof. And sure, he hears from people who have lost weight drinking the sugar water he prescribed, but it is quite possible there are 100 times as many people who didn’t email him because they didn’t see any positive results and decided to try something else. I think the QS stuff is very interesting and helpful on a personal level, but it seems like a stretch to generalize your results to others.

I responded:

I have two responses.

1. Sample size isn’t everything. Sure, a study with n=1 isn’t “scientific proof”. Nor is any other study, in my experience. “Scientific proof” has always required many studies. New scientific ideas have very often started with n = 1 experiments or observations. Later, larger experiments or observations were done. Both the initial n=1 observation and the later n = many observations were necessary for the new idea to be discovered and confirmed.

2. The history of biology teaches there are few exceptions to general rules. See any biology textbook. For example, a textbook might say “lymphocytes fight germs”. This means no serious exceptions have ever been found to that rule. So, as matter of biological history, the person who managed to figure out one particular lymphocyte does turned out to have figured out what they all do. Biology textbooks have thousands of statements like “lymphocytes fight infection” meaning that this sequence of events (you can generalize from one to all, or nearly all) has happened thousands of times. There is no shadow hidden history of biology that teaches otherwise.

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