This is unusually damning to veganism-as-it-is-practiced if not to veganism itself. It would be interesting to see these results across a wide range of diets.
Very large effects are unlikely given the number of long-term vegans who seem to maintain sufficient health. Whereas small effects might be considered a worthwhile sacrifice.
[To clarify: I am not qualified to judge the general healthiness of any particular diet -- any sufficiently popular diet seems to have conflicting studies showing it is "healthy" and others showing it is "unhealthy". The point I intended to make above was that most people either outright reject or remain unswayed by these kinds of studies.]
I don't think a sample size of 21 is especially damning. Nor do I think that the study's authors would come to that conclusion either.
It means that this particular sample of 21 people would have to be extremely atypical under the null hypothesis of no difference. Therefore, given its low sample size (and thus wide standard error), it is 'some' evidence that the effect size is also probably quite large.
The p-value is still the important thing because the p-value is itself affected by the sample size.
Not true (unless I misunderstood what you were trying too say). The probability that a sample will be atypical under the null is exactly the significance level, and does not depend on its size.
What does change with size is that the distribution around the statistic gets more concentrated, meaning your threshold moves to the left, towards lower effect sizes.
Which also means that for smaller sample sizes, it is harder to reach significance, unless you're dealing with a fairly large effect size.
“Veganism is healthy”
To
“Veganism can be healthy if you exercise an impressive amount of restraint, discipline, and judgement in your vegan diet”
Meanwhile, I know lots of people who have given up on vegan diets because they felt like their health was declining, even with regular exercise. I'm sure with enough care and nutritional science they could have gotten it to work. But it's so much easier to just add some animal products to your diet.
* I would not consider it a documentary as it has a clear agenda, but I found it interesting nonetheless.
I definitely favor smaller less impactful scarring, but also, so what? Calling ths "unusually damning" seems like a significant overinflation of concern.
For all we know, it may have far more significant pro-recovery characteristics associated with it. "Oh you built too much scar tissue? Your vegan diet also stitched your blood vessels back together really well."
Please note who wrote this paper, considering what they are famous for, as well as the results: http://web-docs.stern.nyu.edu/pa/kruger_email_ego.pdf