-: Welcome to Module 9.
This module starts our discussion of effect modification
which is also called interaction or moderation.
You'll hear those terms used interchangeably
throughout this module and in epidemiology in general.
If we take a step back,
we've been talking about threats to internal validity
in EPI studies since Module 5.
We started out with bias
and then we spent three modules talking about confounding.
We'll spend the next three modules
talking about effect modification using the same structure.
We'll start here in module 9,
going over the theoretical
and conceptual framework of effect modification.
Then in the next module,
we'll extend that information into SPSS
and the statistical techniques
behind controlling for effect modification.
And then in Module 11,
we'll look at interpreting the results
of effect modification in the public health literature.
Effect modification and confounding are similar in concept
but they're actually very different in practice.
I recommend that you go back
and review your EPI1 notes
just to make sure you feel solid
about the basic difference between the two.
I've included the chapter
from your EPI1 Gordis text on interaction for reading
before you get into your current textbook
because I think it will reinforce that solid grounding
before you dive deeper into the detail and analysis piece.
As always, please reach out with questions,
and I'll see you in the next module.