1. Book: An Introduction to Scientific Research Methods in Geography (Montello & Sutton) 2006 GEOG4020-Research Methods Instructor: Paul C. Sutton University of Denver, Dept. of Geography Prepared by: Katie Williams February 2, 2010 Chapter 7: Experimental & Nonexperimental Research Designs

2. Chapter 7 Overview  Empirical Control in Research  Laboratory vs. Field Settings  Basic Research Designs  Specific Research Designs  Developmental Designs (Change over Time)  Single-Case & Multiple-Case Designs  Computational Modeling  Steps of Computational Modeling 2

3. Learning Objectives  Understand the three forms of empirical control  Physical, assignment, statistical  Distinguish between laboratory & field setting for research  Understands the differences between research designs & their implications for research  Compare computational modeling with traditional experimental research 3

4. Experimental vs. Nonexperimental Studies  Empirical control:  Physical control—physically modified or restricted data collection  Assignment control—creation and control of at least one variable  Statistical control—explicit analysis of main variables of interest 4

5. Experimental Variables  Independent Variable  Manipulated, created  Potential causal variable  Dependent Variable  Not manipulated, measured  Potential effect variable  Confounding Variable  Sheds doubt on validity of casual conclusions 5

6. Laboratory vs. Field  Lab  Man-made, controlled setting  Not necessarily the “chem lab”  Field  Natural, uncontrolled setting  Affects validity of conclusions that general about other settings 6

7. Basic Research Designs  Design choice:  Level of variables  Difference of variables between or within cases  Between-case design  Comparing data between different cases  Within-case (repeated measures) design  Comparing data within the same cases  More efficient, higher precision, reduction of confounds 7

8. Specific Research Designs Non-Experimental  Single Measurement  Multiple Measurement  Posttest-only Design- Single measurement after an event  Pretest-posttest Design- Before and after measurements for comparison  Multiple Pretest-Posttest  Two Group Single Measurement 8

9. Specific Research Designs Experimental  One Group, Manipulated Within  Two Group, Manipulated Within  Two Group, Manipulated Between Posttest Only  Factorial Four Group, Manipulated Posttest Only  Factorial: Manipulating two or more factors (2x2) 9

10. Developmental Designs  Developmental process, change over time  First approach: Cross-sectional (synchronic)  Compare two or more groups of cases at different development stages  Second approach: Longitudinal (diachronic)  Group of cases at same developmental stage compared against itself over time  Hybrid approach: Sequential Design  Compare between and within two or more groups of cases at different development stages over time 10

11. Single-case vs. Multiple-case  Single-case  Repeated-measure design with one case  Studies of single variable effects  Multiple-case  Generalize variance in cases  Reduces potential for error  See causal relationships 11

12. Computational Modeling  Simplified representations of reality  Advantage of whole system representation  Detailed studies of causality, forcing, and feedbacks 12

13. Computational Modeling Steps  1. Create conceptual model  2. Create computational model  3. Run the program  4. Compare model output to empirical data  5. Accept, use, and communicate model 13

14. Discussion  How would you study demographic distribution  How would you ensure empirical control?  What type of experiment would be best?  What experimental design is most practical/cost effective?  Would a computational model be useful in this case? 14

15. Discussion  How would you design an experiment to test: Urban growth? Regional occupational gradients? Species habitat preferences? Point source contamination? Other examples?  How would you ensure empirical control?  What type of experiment would be best?  What experimental design is most practical/cost effective?  Would a computational model be useful in this case? 15