Chapter 4: Basic Experimental Design The Logic of Experimentation A true experiment employs random assignment to 2+ treatment conditions, which allows for subsequent behaviour in each one to be compared with the other. Random assignment: each research participant has the same likelihood of being assigned to either treatment condition as all of the other participants. Control group: closely resembles the experimental group in every way possible except that they do not receive the main factor of interest. Experimental group: gain exposure to the independent variable, which is thought to be responsible for changes in behaviour. Posttestonly group: the dependent variable is introduced only once (i.e. posttest), some time after the IV. Individual differences: unique characteristics we have some are stable (personality) and some are transient (fatigue). While these differences affect our behaviour as individuals, their collective effects are spread evenly between the 2+ groups in an experiment. The advantages of experiments: Careful control: allows researchers to rule out alternative explanations for obtained results and to speculate about the social psychological processes that led to the observed behaviour. Measurement: links overt behaviour with selfreflections or other forms of selfreport (ratings of other people). The identifications of cause: why the introductionremoval of some factor necessarily leads to a predictable outcome. o In social psychology, involves causes that are seen (i.e. behaviours of selfothers) as well as hypothesized causes (i.e. thoughts, feelings, emotions). Developing and testing theory: a web of coherent ideas drawn from critical evaluation of the result develops into a theory, which can then be tested and further refined. Why do experiments matter in social psychology? Social life is too complex to be understood through passive observation or active participation on its own. Planned interference thoughtful introduction of change to assess its effects makes this complexity more manageable. Most social psychology experiments are designed to mimic reallife situations and settings (mundane realism) of the real social world. However, not all research questions lend themselves to experimentation. Turning a research question into a hypothesis: a good hypothesis is Is not a question but, rather, a clear statement. Is reasonably concise. Distinguishes relationships among variables. Is based on what is already known and aimed at expanding this knowledge. Can be easily understood and appreciated by others. Can be tested. Descriptive definition: portrays the relationship among the variables in an abstract way (i.e. measuringinducing positive mood). Operational definition: how abstract concepts are transformed into concrete operations that are amenable to manipulation and measurement (i.e. watching a funny movie in order to induce positive mood). Empirical realizations: how abstract ideas are translated into operational processes of the same variables in similar hypotheses.