Conducting Experiments - DP Home Notes Ch.9 2.27.13...

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DP Home Notes: Ch.9 2.27.13 Conducting Experiments Selecting Research Participants - Method used to select participants can have a profound impact on external validity o EV: the extent to which results from a study can be generalized to other populations and settings - Most research projects involve sampling research participants from a population of interest o Samples may be drawn from the population using probability sampling or nonprobability sampling techniques - Much research is more interested in testing hypotheses about behavior: attempting to detect whether X causes Y rather than describing a population - Determine sample size – increasing sample size increases the likelihood that your results will be statistically significant, because larger samples provide more accurate estimates of population values Manipulating the Independent Variable - Construct an operational definition of the variable - Turn a conceptual variable into a set of operations - Manipulation of the IV is when a researcher changes the conditions to which participants are exposed - The IV and DV must be introduced within the context of the total experimental setting – setting the stage Setting the Stage - Supply the participants with the info necessary for them to provide their informed consent to participate o Includes info about the underlying rationale of the study - If participants know what you are studying, they may try to confirm the hypothesis, or they may try to look good by behaving the most socially acceptable way o Deception may be necessary - Experimental setting must seem plausible to the participants Types of Manipulations Straightforward Manipulations - Researchers able to manipulate an IV with relative simplicity by presenting written, verbal, or visual material to the participants – straightforward manipulations manipulate variables with instructions and stimulus presentations - Most memory research relies on these - Most manipulations of IVs in all areas of research are straightforward Staged Manipulations - Sometimes it is necessary to stage events during the experiment in order to manipulate the IV successfully - The manipulation is then called a staged manipulation or event manipulation
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- Frequently used for 2 reasons: o 1. The researcher may be trying to create some psychological state in the participants, such as frustration, anger, or a temporary lowering of self-esteem o 2. To simulate some situation that occurs in the real world (i.e. Milgram) - These often employ confederates: appears to be another participant, but is actually part of the manipulation - Asch study a good example using confederates and participants - They may be used in field experiments as well as lab research - Staged manipulation demand a great deal of ingenuity and even some acting ability -
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