PSYC 201W Lecture Notes - Lecture 7: Internal Validity, Random Assignment, Sleep Deprivation
2 Sep 2015
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The outline, plan, or strategy used to investigate the research problem: purpose of research design. Suggests how data will be statistically analyzed: goal of research design. Choose the strongest design that is possible, ethical, and feasible. Design in which a treatment condition is interjected between a pretest and posttest of the dependent variable: most threats to internal validity exist, to infer causality must identify and demonstrate that internal validity threats do not exist. O = students" reading measured at beginning of school year[pretest] X = new reading curriculum employed throughout school year. O = students" reading measured at the end of the school year [posttest: threats to internal validity not controlled for. History, testing, regression, instrumentation, and maturation: posttest. Posttest only design with nonequivalent groups example: experimental group = school a adopts new reading curriculum (x, control group = school b uses old reading curriculum, both schools posttest reading at the end of the year (o)
