Unit 1 -- Components of Internal Validity

Intro:

We must carefully evaluate the internal validity of any research study that intends to tell us about causal relationships between behaviors and/or measures. If the study tests attributive or causal hypotheses, then internal validity is not an issue!

Goal:

This exercise will give you practice at identifying the two major components of internal validity

  • Initial Equivalence -- are the participants in the study equivalent on average before the start of the manipulation or treatment?
  • Ongoing Equivalence -- are the procedures the participants undergo equivalent on average during manipulation, task completion and outcome measurement (except for the manipulation or treatment, per se)?

Topics:

There are two topics in this exercise:

  1. Identifying when initial equivalence of measured/subject variables is the internal validity "issue"
  2. Identifying when ongoing equivalence of manpulated/procedural variables is the internal validity "issue"

Reading:

This PowerPoint will describe the major components of external and internal validity and prepare you for the web-based exercise. Internal Validity Types (pdf)

Exercise:

Go to the Psyc350 Canvas section, open the Modules & look in “Unit 1 Pink Things” --  complete the exercise titled  U1 -- Internal Validity Types Prelude

Due Date:

Please have this done before the next lecture -- we will be building on this information then!