This is problematic because it introduces potential confounds.

We have to have random representative samples and no confounds.

But good scientists, good experimentalists, do their best to get no confounds.

Is loathsome in his own deliciousness, And in the taste confounds the appetite

Random representative sampling, independent and dependent variables, double blind, single blind experiments, confounds and causality.

And we have to have no confounds in the experiments. And that's, that's an impossible ideal.

Because in the study I showed you, there might have been confounds. It also wasn't double blind.

And again that's impossible but good experimentalists, we try to do our best to eliminate those confounds.

There are all sorts of possibilities for confounds and in fact, this is truly just a correlational study.

Because I want to introduce the idea, and this is an idea that confounds most students when it's first taught.

And the last possibility is what is known as confounding, because it confounds our ability to figure out what's going on.

And then the idea of confounds. And the most important concept to take away from this segment is the idea of causality.

Dearly bereaved, we gather here in remorse for Rick Johnson... a young man whose death confounds and mystifies us... for Rick was in his prime, beloved by all... exemplary of young men's ideals... and of strong moral fiber.

It's just a correlation between whether someone had a concussion and then things that may happen afterwards.It doesn't mean there's a causal mechanism.There could be all sorts of confounds influencing the relationship between whether someone suffered a concussion and whatever we measure after that.