Published on January 22, 2008
Experimental Designs: Experimental Designs Chee-Wee Tan P1112 Different Types of Methods: Different Types of Methods Research designs are like house blue-prints Designs: Observational Quasi-experimental Experimental Observational Method: Observational Method Obviously, observing! Example: Back pain observation Disadvantages: Long periods of observation No cause-effect information Terminology: Terminology 2 types of variables: Independent Dependent Experimental Designs: Experimental Designs Cause & Effect Difference between experimental & quasi-experimental? Experimental Controlled manipulation of independent variable Quasi-experimental Incomplete control of independent variable Quasi-experimental design: Quasi-experimental design Issues in quasi-experimental design Handwashing example Problems with experimental design In some cases, ethical or practical considerations Quasi-experimental Provides alternative Types of quasi-experimental design: Types of quasi-experimental design One group post-test design One group pre-test/post-test design Interrupted time series design One group post-test design Types of quasi-experimental design: Types of quasi-experimental design Experimental designs: Experimental designs 2 types of experimental designs Between groups / independent measures Repeated measures / within subjects ??? Randomisation: Randomisation Placing participants randomly into the groups Purpose: prevent our own bias in influencing allocation Do stats and prosper! I love stats Between group designs: Between group designs Different groups of participants for different conditions Advantages: Simple Practice and fatigue not a problem Between group designs: Between group designs Disadvantages: More tedious Less sensitive to detect any experimental effects Examples of between group designs: Examples of between group designs Post-test only / control group design Pre-test / post-test control group Repeated Measures: Repeated Measures Participants allocated to all conditions Advantages: More economical More sensitive in detecting effects Disadvantages: ‘Carry over’ effect Intervention must be reversible More designs: More designs Multiple levels of the independent variable designs Multi-factorial designs Latin square designs Multivariate designs Single-subject experimental designs Why are research designs important?: Why are research designs important? Exclude unknown factors Makes it easier for interpretation A warrior knows his research designs as intimately as his own weapon……..Grrrrrr Me!