[Dylan16807]

That's an entirely different question from ethics.

But paying people to be studied tends to be effective.

[kjhcvkek77]

I don't think so. Managing the relationships with the public and study participants is an important part of the ethics.

[Dylan16807]

Ethics and managing relationships with the public overlap.

But I don't think the particular aspect of "making sure you have enough participants" interacts very much with ethics. Especially when the failure state in question is an honest failure to attract them.