Internal vs. External Validity

What is internal validity?

Extent to which the experiment shows the changes in the behavior are due to the independent variable and not the result of uncontrolled or confounding variables 

Examples of confounding variables:  

-Starting medication

-Change in home life (divorce, death, new baby, move, etc)

-Change in school/therapy life (new therapists, clinicians, new building, new school, etc.)

What is external validity?

The degree to which a study's findings have generality to other subjects, settings, and/or behaviors

-Will this study prove effective if a different population of participants is used?

-Will this study be effective if used with a different type of behaviors?

If the study was done in a clinic, will it be effective if conducted in a school classroom setting?  What about in a home environment?

Resources:  Cooper J.O, Heron T.E, Heward W.L. Applied behavior analysis (2nd ed.) Upper Saddle River, NJ: Pearson; 2007.

Testing a Definition

So now that you have learned the characteristics of a good definition, how do you test to see if your definition is actually good?

Cooper, Heron, and Heward describe a few questions and answers to determine if you have a good definition.

1.  Can you count the number of occurrences?

-You should be able to answer "Yes"

2.  Will a stranger know what to look for based on the definition alone?

-You should be able to answer "Yes"

3.  Can you break the target behavior down to smaller,  more specific components?

-You should answer "No"

-The target behavior should already be broken down into the most specific components as possible

Resources:  Cooper J.O, Heron T.E, Heward W.L. Applied behavior analysis (2nd ed.) Upper Saddle River, NJ: Pearson; 2007.