CH09 business methodology

**Chapter 9Experimental Designs 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Causal ResearchResearch conducted to identify cause-and-effect relationships among variables when the research has already been narrowly defined

* 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Evidence for CausalityCovariationEvidence of the extent to which X and Y occur together or vary together in the way predicted by the hypothesisTime order of occurrence of variableEvidence that shows X occurs before YElimination of other possible causal factorsEvidence that allows the elimination of factors other than X as the cause of YA logical explanationAbout why the independent variable affects the dependent variable.


ExperimentData collection method in which one or more IVs are manipulated in order to measure their effect on a DV, while controlling for exogenous variables in order to test a hypothesis

Cause and effect relationship is established byManipulation of independent variableControlling for exogenous factors* 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Manipulation of IVManipulationCreation of different levels of the IV to assess the impact on the DV

Treatment levelsThe arbitrary or natural groups a researcher makes within the IV

Evidence for causalityCovariation (difference between groups)Time order control* 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Exogenous VariablesControlling for exogenous/confounding variablesEliminating other possible causal factorsEliminating alternative explanations

Experimental designs available

Two types of exogenous variablesRelated to participantsRelated other, environmental factors* 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Related to ParticipantsSelection bias: improper assignment of participants to the experimental groups Matched groups: Match the different groups as closely as possible in terms of age, interest, expertise etc. Random assignment: Randomly assign members to different treatment groups. The differences will be randomly distributed. Systematic bias will reduce.Statistical control: Measuring the external variables and adjusting for their effect through statistical methods

Mortality: Loss of participants during the experiment* 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Related to other actorsHistory effects: External events occurring at the same time that may affect the DVMaturation effects: Changes in the participants as a passage of time that may affect the DVTesting effects: The experiment itself affect the responses Main testing effect: prior responses affect later responses Interactive testing effect: prior responses affect perception of IVInstrumentation effects: Changes in measuring instrument* 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Experimental Design* 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Exercise*An organization would like to introduce one of two types of new manufacturing processes to increase the productivity of workers. Both involve heavy investment in expensive technology. The company wants to test the efficacy of each process in one of its small plants.

Propose an experiment, using:- Pretest posttest control group design- Posttest control group designAnd calculate for each design the specific effect of each new process on the productivity. 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

Validity Internal validityDetermination of whether the effect is actually caused by the manipulation of treatments and not by other, exogenous variables

External validityDetermination of whether the cause-and-effect relationships found in the experiment can be generalized


AdvantagesHigh degree of controlHigh internal validity / replicationLess costly and less expensive

DisadvantagesArtificiality => reactive errorDemand artifactsLower external validity*Compared to field experiments, lab experiments have the following 2009 John Wiley & Sons Ltd.www.wileyeurope.com/college/sekaran

CH09 business methodology

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