I am not sure if I’m a fan of this, because the true effect of an intervention will vary across place in ways that will affect the results of future studies, but shouldn’t affect our assessment of deworming in this context. So future studies might extend deworming to countries where worm burdens are lower and thus find lower effects of deworming. But it would be a mistake to conclude that deworming in Kenya is less effective based on those studies.
You might say we can control for the country being studied, but that is only the case if there are many studies in one country, which is rarely the case.
I am not sure if I’m a fan of this, because the true effect of an intervention will vary across place in ways that will affect the results of future studies, but shouldn’t affect our assessment of deworming in this context. So future studies might extend deworming to countries where worm burdens are lower and thus find lower effects of deworming. But it would be a mistake to conclude that deworming in Kenya is less effective based on those studies.
You might say we can control for the country being studied, but that is only the case if there are many studies in one country, which is rarely the case.