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Chapter 9 PsyB01.doc

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Connie Boudens

Chapter 9 Conducting Experiments Selecting Research Participants - Research projects involve sampling research participants from a population of interest; the population is composed of all of the individuals of interest to the researcher - Samples may be drawn from the population using probability sampling or nonprobability sampling techniques: o When it is important to accurately describe the population, you must use probability sampling (e.g. scientific polls) o When the focus of the study is the relationships between the variables being studied and testing predictions derived from theories of behaviour, the participants may be found in the easiest way possible using nonprobability haphazard or convenience sampling methods Nothing is wrong with such methods as long as you recognize that they affect the ability to generalize your results to some larger population Manipulating the Independent Variable - To manipulate an independent variable, you have to construct an operational definition of the variable o An operational variable is turning a conceptual into a set of operations specific instructions, events, and stimuli to be presented to the research participants - setting the stage is introducing the independent and dependent variables within the context of the total experimental setting Setting the Stage - In setting the stage, you usually have to do two things: providing the participants with the informed consent information needed for your study and explain to participants why the experiment is being conducted (although you dont tell them the particular hypothesis) - If participants know what you are studying, they may try to confirm the hypothesis, or they may try to look good by behaving in the most socially acceptable way o If you find deception is necessary, you have to address the deception when you debrief the participants at the conclusion of the experiment - There are no clear-cut rules for setting the stage, except that the experimental setting must seem plausible to the participants, nor are there any clear-cut rules for translating conceptual variables into specific operations Types of Manipulations Straightforward Manipulations - Researchers are usually able to manipulate a variable with relative simplicity by presenting written, verbal, or visual material to the participants o Such straightforward manipulations manipulate variables with instructions and stimulus presentations - Most memory research relies on straightforward manipulations - Most manipulations of independent variables in all areas of research are straightforward; researchers vary the difficulty of the material to be learned, motivation levels, the way questions are asked, characteristics of people to be judged, and other factors in a straightforward manner Staged Manipulations - A staged or event manipulation is when it is necessary to stage events that occur during the experiment in order to manipulated the independent variable successfully - Staged manipulations are most frequently used for two reasons: o 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 A staged manipulation may be necessary to stimulate some situation that occurs in the real world - Staged manipulations frequently employ a confederate (sometimes termed an accomplice); usually, the confederate appears to be another participant in an experiment but is actually part of the manipulation o A confederate may be useful to create a particular social situation - Confederates may be used in field experiments as well as laboratory research - Staged manipulations are used to involve the participants in an ongoing social situation, which the individuals perceive not as an experiment but as a real experienceo Researchers assume that the result will be natural behaviour that truly reflects the feelings and intentions of the participants - However, such procedures allow for a great deal of subtle interpersonal communication that is hard to put into words; this may make it difficult for other researchers to replicate the experiment - Also, a complex manipulation is difficult to interpret; if many things happened during the experiment, what one thing was responsible for the results? - In general, it is easier to interpret results when the manipulation is relatively straightforward, but the nature of the variable you are studying sometimes demands complicated procedures Strength of the Manipulation - A general principle to follow is to make the manipulation as strong as possible; a strong manipulation maximizes the differences between the two groups and increases the chances that the independent variable will have a statistically significant effect on the dependent variable - A strong manipulation is particularly important in the early stages of research, when the researcher is most interested
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