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8/14/2019 Lecture 4. Experiments and Causal Design
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
Lecture 4.Lecture 4.
Experiments andExperiments andcausal designcausal design
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
Learning objetivesLearning objetives
To understand what are experiments in theTo understand what are experiments in the
economy and in business.economy and in business. To know different types of experiments andTo know different types of experiments and
their lacks.their lacks.
To identify variables that can affectTo identify variables that can affectexperimental designs.experimental designs.
How to design true causal experiments.How to design true causal experiments.
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
1. Causality and experiments1. Causality and experiments
CausaltyCausalty; one fact is the consequence of another.; one fact is the consequence of another. ExperimentExperiment; setting the conditions to identify; setting the conditions to identify
causal relations.causal relations. Direct experimentDirect experiment; a theory supports the; a theory supports the
experiment.experiment. Indirect experimentIndirect experiment; there are not supporting; there are not supporting
theories to explain causal relations.theories to explain causal relations. Independent variablesIndependent variables; variables under control.; variables under control. Dependent variablesDependent variables; reacting variables to causes.; reacting variables to causes. Proof unitsProof units; the reacting persons, products, brands,; the reacting persons, products, brands,
and so on.and so on. ValidtyValidty..
InternalInternal; a cause has one effect.; a cause has one effect. ExternalExternal; if the same cause allways generates; if the same cause allways generatesthe same effect.the same effect.
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
ExperimentExperiment
Is a scientific investigation inIs a scientific investigation in
which the investigator manipulateswhich the investigator manipulatesvariable/s to observ variations invariable/s to observ variations inother/s variables.other/s variables.
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
2. Conditions for experiments2. Conditions for experiments
Facts happen along the time. The causeFacts happen along the time. The cause
alwaysalways foregoesforegoes the consequence.the consequence.
ConcomitantConcomitant variation. Facts happen within avariation. Facts happen within avery shot time period.very shot time period.
Extraneous variablesExtraneous variables must be isolated.must be isolated.
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
ValidityValidity
Internal validity: there is anInternal validity: there is anobserved cause-effect relation.observed cause-effect relation.
External validity: the relationExternal validity: the relationcan be generalized.can be generalized.
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
3. Extraneous variables3. Extraneous variables
History.History.
Maturity.Maturity.
Main effect.Main effect.
Interactive effect.Interactive effect.
Testing effect or Instrumental effectTesting effect or Instrumental effect RegressionRegression
Bias in selecting the unitsBias in selecting the units
Mortality.Mortality.
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
Controlling extraneous variablesControlling extraneous variables
Units must be randomly selected.Units must be randomly selected.
Units must be similar.Units must be similar.
Use experimental designs.Use experimental designs.
Use statistics for data treatment.Use statistics for data treatment.
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
4. Some experimental designs4. Some experimental designs
Designs
Preexperimental Experimental Statistical Laboratory
One shotcase study
One groupPretest
Postest
Staticcomparison
GroupsControlPretestPostest
4 groupsSolomon
Random
Random
Blocks
Latin square
AbelsonKellyAschTaylor
Blind testsAd test
Sketching
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
5. Laboratory experiments5. Laboratory experiments
Blind test.Blind test.
Ad test (pre-post)Ad test (pre-post)
Sketching.Sketching. Abelson test.Abelson test.
Kelly grid technique.Kelly grid technique.
Taylor experiment.Taylor experiment.
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Control pretest-postestControl pretest-postest
EG: R1 ------------> R2CG: R3 ------------> R4
The experiment effect is measured,(R2 - R1) - (R4 - R3)
R2 - R1 = experiment effect+ interactive effectinteractivo + main effect + history + maturity +
testing bias + regression + mortality
R4 - R3 = main effcet+ history + maturity + testingbias + regression + mortality
(R2 - R1) - (R4 - R3) = experiment effect+ interactiveeffect
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Fundamentos y Tcnicas. 10 Ed. I. Grande y E. Abascal
7. Statitiscal experimental design7. Statitiscal experimental design
RandomRandom ; one variable under control;; one variable under control;
priceprice oror ad budget.ad budget.
Random block;Random block; two variables undertwo variables undercontrol; pricecontrol; price andand package.package.
Latin squareLatin square; three variables under; three variables under
control; prices, ad and package.control; prices, ad and package.
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Random experimentRandom experiment
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ResultsResults
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Random blocksRandom blocks
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ResultsResults
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Latin squareLatin square
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Latin squareLatin square
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ResultsResults
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Assesing experimental methodAssesing experimental method
Statistical lacksStatistical lacks.. Data must be normally distributed.Data must be normally distributed.
Data are expected to be homodedastic.Data are expected to be homodedastic.
Effects are considered aditive.Effects are considered aditive.
It is difficult to isolate the experimental conditions.It is difficult to isolate the experimental conditions. Markets.Markets.
Short term.Short term.
Competitors can react and interfere.Competitors can react and interfere.
Experiments are expensive.Experiments are expensive.
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