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Chapter 8


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PSYC 2030
Krista Phillips

PSYCH-INTRO TO RESEARCH METHODS LORENZ SOL CHAPTER 8 NONRANDOMIZED RESEARCH AND CAUSAL REASONING HOW IS CAUSAL REASONING ATTEMPTED IN THE ABSENCE OF RANDOMIZATION  Prospective data is collecting data by following one’s reaction forward in time. Commonly used in longitudinal research, the defining characteristic of such research being that individuals are observed and measured repeatedly through time.  Retrospective data is data collected back in time. QUASI-EXPERIMENTAL RESEARCH  Campbell and Stanley coined the expression quasi-experimental research to describe all the different types on nonrandomized research for generalized causal inference. Quasi merely means, “resembling.” This research often resembles randomized experimental research because quasi experiments have outcome measures, sampling units, and something comparable to the experimental treatment (i.e.,an intervention), but what identifies them as quasi-experimental is that they do not randomly assign individual units to treatment conditions. WHAT IS THE “THIRD-VARIABLE” PROBLEM?  Third-variable problem is correlated with both X and Y is the reason X and Y covary. A third variable that is correlated with both X and Y can also account for the correlation between X and Y. HOW CAN CAUSAL EFFECTS BE STUDIED IN NONEQUIVALENT GROUPS?  Nonequivalent-groups design are traditionally between-subjects designs in which the sampling units (subjects, groups, etc.) are allocated to experimental and control groups by means other than randomization and are observed or tested before and after the experimental treatment.  Subclassification on propensity scores reduces all of the variables on which the “treated” and “untreated” subjects differ into a single composite variable. This composite variable, called a propensity score, is a summary statistic of all the differences on all variables on which the “treated” and “untreated” subjects differ. Actual procedure requires a computer program. WAIT-LIST CONTROL GROUPS  Wait-list control group gives information about the immediate and delayed effect of the treatment as well as a replication of the immediate effect. WHAT ARE TIME-SERIES DESIGNS AND “FOUND EXPERIMENTS”?  In time series designs, the defining characteristic is the study of variation across some dimension over time.  When the effects of some intervention or “treatment” are inferred from a comparison of the outcome measures obtained at different time intervals before and after the intervention, the data structure is called an interrupted time-series design.  The term time series means there is a data point for each point in time, and an interrupted time series means there is a dividing line at the beginning of the intervention (a line analogous to the start of the “treatment”)  David P. Phillips referred to his studies as “found experiments” because they are essentially found (or discovered) in naturally occurring situations. PSYCH-INTRO TO RESEARCH METHODS LORENZ SOL WHAT WITHIN-SUBJECTS DESIGNS ARE USED IN SINGLE-CASE EXPERIMENTS?  A family of nonrandomized designs that is also a mainstay of behavior modification research is single-case experimental research (also called small-N experimental research and N-of-1 experimental research).  These designs are conceptualized as a subcategory of interrupted time- series designs. They incorporate “treatments” (interventions) that are manipulated and controlled for within a repeated-measures design.  In single-case experiments, [a] only one sampling unit is studied, or only a few units are studied; [b] repeated measurements are taken of the unit (a within-subjects design); [c] random assignment is rarely used.  Behavioral baseline—pretest—is the observations of a consistent pattern in the subject’s behavior before the experimental treatment or intervention. That is, a relatively stable pattern of behavior before the treatment or intervention serves as a kind of “pretest” with which details about the pattern of behavior after the treatment can be compared. In this way, the unit serves as its own control in a within-subjects design.  Single-case researchers use a different notation system to represent their specific designs. The basic model is called an A-B-A design, whic
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