10 - experimental research - one-way designs

10 - experimental research - one-way designs -...

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Unformatted text preview: Demonstration of Causality 21:27 Association Before we can infer that the former causes the latter, there must first be an association between an independent and a dependent variable The causal relationship between variables in behavioral science are probabilistic Temporal Priority If event A occurs before even B, then A could be causing B o If event A occurs after event B, it cannot be causing that event Control of Common-Causal Variables To make causal statements requires the ability to rule out the influence of common-causal variables that may have produced spurious relationships between the independent and dependent variables o Experimental manipulations: The researcher can rule out the possibility that the relationship between the independent and dependent variable is spurious One-Way Experimental Designs 21:27 One-way experimental design: Has one independent variable The Experimental Manipulation Manipulated: To guarantee that the independent variable occurs prior to the dependent variable, in experimental designs the independent variable or variables are created o The manipulation becomes the independent variable o Levels: The specific situations that are created within the manipulation o Conditions: The levels of the independent variables Equivalence and Control o An experimental manipulation allows the researcher to rule out the possibility of common-causal variables The influence of common-causal variables is eliminated through creation of equivalence among the participants in each of the experimental conditions Between-participants design: Using different but equivalent participants in each level Repeated-measures design: Using the same people in each of the experimental conditions Random Assignment to Conditions o Random assignment to conditions: The most common method of creating equivalence among the experimental conditions Involves the researcher determining separately for each participant which level of the independent variable she or he will experience Done through a random process Involves the researcher drawing separate simple random samples of participants to be in each of the levels of the independent variable o Random assignment to conditions ensures that the average score on all variables will be the same for the participants in each of the conditions Greatly reduces the likelihood of differences Selection of the Dependent Variable Experiments have one or more measured dependent variable designed to assess the state of the participants after the experimental manipulation has occurred One-Way Experimental Designs...
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This note was uploaded on 11/16/2010 for the course PSYC 420 taught by Professor Staff during the Fall '08 term at Maryland.

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10 - experimental research - one-way designs -...

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