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University of Toronto Mississauga

Chapter 2: The Scientific Method in Psychology • Goal of quantitative/ psychology is the explanation of behaviour • Need language that is precise enough to be understood by others and general enough to apply it to a variety of situations – this language takes the form of explanations which are general statements about events that cause phenomena to occur • Scientific method – agreed-upon approach to discovery and explanation o Set of rules that dictate general procedures a scientist must follow in research o Rules are based on logic and common sense • Three types of scientific research: • Naturalistic observations – observation of behaviour of people or animals in their natural environment o Least formal and constrained by fewest rules o Provide foundation of biological and social sciences • Correlational studies – examination of relations between 2+ measurements of behaviour or other characteristics of people or animals o Involve more formal measurements of environmental events, of individuals’ physical and social characteristics, and of their behaviour • Experiments – study which researcher changes value of an independent variable and observes whether this manipulation effects value of dependent variable o Only research which can confirm existence of cause-and-effect relations among variables Five steps summarizing the rules of scientific method: 1. Identify the problem and formulate hypothetical cause-and-effect relations among variables  Involves identifying variables (behaviours and environmental and physiological events) and describing relations among them in general terms 2. Design the experiment  experiments involve manipulation of independent variables and observation of dependent variables  each variable must be operationally defined and independent variable must be controlled so that it is only thing responsible for changes to dependent variable 3. Perform experiment  organize material, train people to perform it, recruit volunteers, randomly assign volunteers to experimental group of control group 4. Evaluate hypothesis by examining data from study  Involves special mathematical procedures used to determine whether observed effect is statistically significant 5. Communicate results  Article, conferences, conventions • Replication – repetition of an experiment or observational study to see whether previous results will be obtains; uncovers statistical anomalies and incompetently conducted research • Great scientific research occurs as result of long-term research programs in which findings are part of collective endeavour • Psychological research in Canada is supported by:  Natural Sciences and Engineering Research Council  Social Sciences and Humanities Research Council  Canadian Institutes of Health Research (Medical Research Council) Step 1: Identifying the Problem • Hypotheses - statement, usually designed to be tested by an experiment, that tentatively expresses a cause-and-effect relationship between 2+ events • Theory – set of statements designed to explain a set of phenomena, proposes relationships among variables, and makes new predictions; more encompassing than a hypothesis  way of organizing system of related hypotheses to explain some larger aspect of nature  generates testable hypotheses - ones that can be supported or proved wrong by scientific research • framework for most psychological research is larger in scope than hypothesis but smaller in scope than full-fledged theory Naturalistic Observations • Naturalistics – people who carefully observe animals in their own environment, disturbing them as little as possible; observer remains in background Step 2: Designing an Experiment • Variables – anything capable of assuming any of several values (very in value) • Manipulate – setting values of an independent variable in an experiment to see whether value of another variable is affected • Experimental Group – group of participants in an experiment, members of which are exposed to particular value of independent variable, which has been manipulated by researcher • Control Group – comparison group used in experiment, members of which are exposed to naturally occurring or zero value of independent variable • Variable – anything capable of assuming any of several values • Independent variable – variable that is manipulated in experiment as means of determining cause-and-effect • Dependent variable – variable that is measured in experiment as means of determining cause-and-effect relations  value of dependent variable depends on value of independent variable  independent and dependent variables are categories into which various behaviours are classified  experiment is performed by manipulating value of independent variable and observing whether change affects dependent variable • Nominal Fallacy – false belief that one has explained causes of phenomenon by identifying and naming it; (explaining lazy behaviour by attributing it to “laziness”) • Operational Definitions – translation of generalities into specific terms; definition of a variable in terms of operations the researcher performs to measure or manipulate it • Validity -degree to which operational definition of a variable reflects variable it is designed to measure or manipulate; how appropriate it is for testing researcher's hypothesis  used to develop manipulations and measures of a vast array of psychological concepts  if different investigators define variables in slightly different ways but explanations yield similar results, we become more confident that we are approaching good explanation of phenomena we are studying • confound – fail to distinguish • Confounding Variables – inadvertent simultaneous manipulation of more than one variable; results of an experiment involving confounded variables permit no valid conclusions about cause-and-effect • Counterbalancing – systematic variation of conditions in an experiment, such as order of presentation of stimulus, so that different participants encounter them in different orders; prevents confounding of independent variables with time-dependent processes such as habituation or fatigue Step 3: Performing an experiment • Reliability – repeatability of a measurement; likelihood that if measurement was made again it would yield same value • Interrater Reliability – degree to which 2+ independent observers agree in their ratings of another organism's behaviour • Random Assignment – procedure in which each participant has an equally likely chance of being assigned to any of the conditions or groups of an experiment  Used to avoid confounding participant characteristics with manipulated values of an independent variable • Single-blind study – one participant receives a placebo – participant doesn’t know value of independent variable • Double-blind study – neither participant and researcher know value of independent variable Correlational Studies • For each member of a group of people we measure 2+ variables as they are found to exist, and determine whether variables are related by using a statistical procedure correlation o Often used to study effects of personality variables on behaviour • Matching – systematic selection of participants in groups
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