[estearum]

If you actually copy/pasted the "quoted" text from my comment, you will have found I said something different from what you claimed.

Virtually any study has an obvious potential for selection bias. That's why people write up how they did the study and then other people can interrogate and criticize it.

Might as well just paste a link to https://en.wikipedia.org/wiki/Bias_(statistics)#Types in every comment section ever.