So why do you still take vitamins? If you look at their Figure 2, there aren’t many studies that ‘favored antioxidants’, and some of those studies had low doses.
“A linear analysis assumes that if 10 milligrams is good for you, then 100 milligrams is ten times as good for you, and 1000 milligrams is one-hundred times as good for you.” That’s only true if the range of data included both 10 milligrams and 1000 milligrams. Linearity is only assumed within the range of data of the data sets.
The hockey stick approach seems too restrictive as well. Just use a p-spline.
There doesn’t appear to be statistician on the paper. This study really needed one. Using meta-regression to estimate a dose effect is challenging, especially when you don’t have access to the original data (just using aggregate, study-level covariates). In fact, the dose effect and the concept of study heterogeneity are conflated here.
I agree with you that it’s unclear what they actually did.
So why do you still take vitamins? If you look at their Figure 2, there aren’t many studies that ‘favored antioxidants’, and some of those studies had low doses.
“A linear analysis assumes that if 10 milligrams is good for you, then 100 milligrams is ten times as good for you, and 1000 milligrams is one-hundred times as good for you.” That’s only true if the range of data included both 10 milligrams and 1000 milligrams. Linearity is only assumed within the range of data of the data sets.
The hockey stick approach seems too restrictive as well. Just use a p-spline.
There doesn’t appear to be statistician on the paper. This study really needed one. Using meta-regression to estimate a dose effect is challenging, especially when you don’t have access to the original data (just using aggregate, study-level covariates). In fact, the dose effect and the concept of study heterogeneity are conflated here.
I agree with you that it’s unclear what they actually did.