Child Development 133 
Research Methods in Human Development

Sections 04, 68, & 69
Hembree           Spring, 2011


External/Ecological Validity

I. External Validity

A. Introduction

= ability to generalize your experimental results




B. Three types of generalization:

1. to the population of interest



2. to the environment of interest




3. to the time of interest





C. Threats to External Validity

1) threats based on methods





2) threats based on participants




  D. Replication

1. Exact replication






2. Conceptual replication




E. Ecological Validity






F. What can we do to improve external and ecological validity? Why should we bother?





II. Discussion Questions





Send problems, comments or suggestions to:

California State University, Sacramento
College of Education
Department of Child Development

Updated: January, 2011