Child Development 133 
Research Methods in Human Development

Sections 02 & 06
Hembree            Fall, 2009


  Experimental Design

I. Introduction

Design = Plan of Experiment ("blueprint")

Ask questions:

1) How many variables to test?  


2) How many levels for each variable?  


3) How to compose groups?



II. Pre/Post-test designs  

A. Case study




B. One-group pre-posttest design




C. Non-equivalent control group  




D. Quasi-experimental designs  




III. (True) experimental design 


A. Levels and variables  




B. Simple, two-group design


  •  experimental group 


  •   control group



C. How do we assign subjects?

1. Random assignment





2. Correlated assignment

a. matched pair

b. natural pairs

c. repeated measures


D. Repeated measures designs



  • Advantages and disadvantages


E. Increasing the complexity of designs

1. Increase the number of levels of a variable


2. Increase the number of dependent variables


3. Increase the number of Independent Variables Factorial Designs




 IV. Factorial Designs

  • Increasing the complexity by increasing the number of Independent Variables 

A. Advantages of factorial designs



B. Main effects vs. interaction effects

MAIN EFFECTS the effects of one variable, ignoring (averaged across) the other


INTERACTION EFFECTS the effects of the variables together

Does one variable CHANGE the effects of another?



C. Interaction effects 

an example:...


Time of Day







2 cups




1. What are some hypotheses we could make?


2. Possible outcomes:

  • Main Effects ONLY





  • Interaction Effects





3. What would both main effects and interaction effects look like?




D. Interpreting Interaction Effects

   DISCUSSION/ACTIVITY (HOMEWORK 8 - completed in class)


  E. Statistics for multiple group means (ANOVA)




Send problems, comments or suggestions to:

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

Updated: August, 2009