I worry the planned recruitment of 3000 was either plucked from the air or decided on due to budget constraint
I want to be careful not to speak for the authors here, but I’m personally pretty sure it was picked by budget constraint, though with an eye to power calculations (that I saw, not sure why they weren’t published) suggesting it would be sufficient.
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Given the large temporal fluctuations (e.g. the large reduction in control group), the pretty modest effects, I remain sceptical—leave alone the obvious biases like social desirability etc.
Agreed.
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Another reanalysis which might reassure would be monte carlo permutation of food groups: if very few random groups show reduction in consumption to a similar magnitude as meat, great (and, of course, vice versa).
I want to be careful not to speak for the authors here, but I’m personally pretty sure it was picked by budget constraint, though with an eye to power calculations (that I saw, not sure why they weren’t published) suggesting it would be sufficient.
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Agreed.
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In my re-analysis, I did make a “bogustarian” label looking at reduction in beans, fruits, nuts, vegetables, and grains and found no statistically significant results (see https://github.com/bnjmacdonald/reducetarian-messaging-study/blob/master/peter-reanalysis/analysis.R#L124-L132). So maybe that’s reassuring, but one could extend this to be a true monte carlo method.