[FeepingCreature]

Simpson's paradox: analyzing trends per subgroup can give a different result than pooled data.

Berkson's paradox: analyzing a single subgroup selected with a function aggregating two traits (additively?) will indicate an anticorrelation between the traits.

Simpson's paradox says you can't judge group trends from subgroup trends. Berkson's paradox says given a group selected in a specific way, it will have a certain property in itself. They're just different statements.

[Pyramus]

Yes and no.

Berkson's paradox is a special case of Simpson's for the two subgroups selected and non-selected.

The difference is that Berkson's paradox involves selecting the subgroup a posteriori and in a particular way, Simpson's paradox assumes a selection a priori.

[kgwgk]

Another difference is that Simpson's "paradox" involves all the subgroups that the full population is partitioned into, unlike Berkson's "paradox".

[junippor]

I like how you put paradox in quotes. I also annoys me when people call these things paradoxes. They're more properly called counter-intuitive phenomena. I wonder if there's a single-word name for that.

[kgwgk]

paradox :-)

[junippor]

So I actually checked and... turns out you're right.

According to Wikipedia, "paradox" can either mean "logically self-contradictory statement" or a "statement that runs contrary to one's expectation". I always thought that it meant the former only.

These two concepts should really really have separate words.

[getlawgdon]

You "checked Wikipedia," is that it? You're done now?