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Chapter 8

PSYB01 Chapter 8 notes + key terms for exam prep.doc

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Department
Psychology
Course
PSYB01H3
Professor
David Nussbaum
Semester
Fall

Description
Chapter 8: Quasiexperimental and Nonexperimental Designs •What allows us to label single and multifactorial experiments as true = randomization o Between subject - means randomly assigning participants to different conditions or levels of the independent variables o Within subject - means participants receive all levels or conditions of the independent variables in a randomized or counterbalanced order Quasiexperimental Design •Gender, race, age, ethnicity, socio-economic status (SES), locale, diagnosis, personality traits, and personal history are just some examples of independent variables that are not possible for an experimenter to directly manipulate •When particular individual characteristics are used for the bases of selecting research participants, an experimenter is often interested in studying the effects of these subject variables on a dependent measure o Here a subject variable such as gender is treated as a type of independent variable •When exposures to events, situations, or settings that emanate from the 'real world' define how participants are selected, we refer to this type of independent variable as a natural treatment •Independent variables of true experiments are completely controlled ad directly manipulated by the experimenter •Subject variables and natural treatments belong to a distinct class of independent variables that many behavioural researchers term "quasi-independent" o A quasiexperiment is one that investigates the effects of quasi-independent variable on a dependent variable o An experimenter can directly control and manipulate one or more of the independent variables o Quasiexperiments offer a fertile research designs for investigating some of the most important and creative questions in psychology •Nonequivalent-control-group designs: nonequivalent-control-group designs have experimental and comparison groups that are designated before the treatment occurs and are not created by random assignment •Before-and-after designs: before-and-after designs have a pretest and posttest but no comparison group. In other words, the participants exposed to the treatment serve, at an earlier time, as their own controls Natural Treatments as Quasi-Independent Variables •Natural treatments fall into the class of quasi-iandependent variables that cannot be directly manipulated; o Researcher can provide only an "after-the-fact" or ex post facto analysis Subject Variables as Quasi-Independent Variables •Mixed factorial designs combines both between and within subjects factors Nonequivalent-control-group-designs •Random assignment provides us with the best chance of ensuring that the groups would be equivalent at the beginning of the experiment before the treatment or the manipulation of the independent variable •Groups are selected on the basis of pre-existing, immutable subject characteristics or exposure to some kind of natural treatment The control group can never be considered to be equivalent to the experimental group • •Pre-existing differences cannot be equalized by random assignment as would be the case in a true experiment o The most common quasiexperiment is referred to as a nonequivalent control group design • Have experimental and control groups that have been predetermined or predesignated by either an existing subject characteristics or an already occurred natural treatment that are not created by random assignment •Quasiexperimental studies with nonequivalent control or comparison groups often receive high marks for their external validity in general, and their ecological validity in particular o Are often high in generalizability and high in realism Matching •Two methods of selection of a control group can be used: individual matching and aggregate matching o Individual matching: individual cases in the treatment group are matched with similar individuals in the control group • Can create a control group that is very similar to the experimental group •When rndom assignment is not possible, the second method of matching makes mores sense: identifying a comparison group that matches the treatment group in the aggregate rather than trying to match individual cases o Referred to as aggregate matching: it means finding a comparison group that has similar distributions as key variables •A researcher matches on a variable that is highly related to the dependent variable o A researcher can collect pretest measures and then match participants either individuals or in the aggregate on pretest scores •regression artifact - can occur anytime a pretest measure is used for matching •When retested on that same ability earn sores that are closer to the mean of their group than were the original scores - regression to the mean o May be confounding factor for interpreting results of studies that match groups on pretest measures o Is important to consider whenever random assignment is not or cannot be used and groups are matched on a pretest measure Before and After Designs •Most common feature - absence of a comparison group •All cases are exposed to the experimental treatment o Basis for comparison is provide by comparing the pretreatment to the posttest measures o Simples types = fixed sample panel design (one pretest and one posttest) •Interrupted time series design is often used in quasi-experimental research to examine observations before and after a naturally occurring treatment o Simplest time series design - there is a single experimental group for which we have obtained multiple observations before and after a naturally occurring treatment •Multiple group before and after design o Several before and after comparisons are made involving the same independent and dependent variables but with different groups •Another type - involves multiple pretest and posttest observations of the same group o Repeated measures panel designs which include several pretest and posttest observations • Are stronger than simple before and after panel designs because they allow the researcher to study the process by which an intervention or treatment has an impact over time o Time series designs • Compare the trend in the dependent variable up to the date of the intervention or event whose effect is being studied and the trend in the dependent variable after the intervention • Particularly useful for studies of the impact of new laws or social programs that affect everyone and that are readily assessed by some ongoing measurement Correlational Relationships •Quasi-experiments lack design features that improve internal validity, thus lessening coincidence in causal conclusions •Researchers are often interested in examining the relationship between variables • Degree and direction of a relationship between two variables can be tested with a single statistic known as a correlation coefficient o r o Can vary from ~1.00 through 0.00 - +1.00 o Number value = indicates strength of relationship • Larger = stronger o Regardless if number is positive or negative Refers to direction •  Positive = as one variable increases, the other does too  Negative = indicates that as one variable increases, the other decreases • Scatter diagrams are used to graph correlations o Graph of correlation - correlation always involves 2 variables • An interaction occurs when the effects of one independent variable depend son the level of another independent variable • Crossover two way interaction - two independent variables that exert different effects on the dependent variable, which when plotted in a graph reveal lines that cross over each other Control and Natural Treatments • Most experiments have either a control group (between subjects design) or a control condition (within subjects design) • A key characteristic of a control condition is that it provides a baseline against which an important variable of an experiment can be compared Quasi-experimental research of Culture and Cognition • Culture is traditionally studied using nonexperimental research designs o Can involve a variety of research techniques and designs - ethnographic studies, correlational analyses and qualitative investigations Constructivist Theories of Culture • In constructivist theory, culture is conceptualized as the rich blend of images, metaphors, practices and discourses about human life that prevail in a given group or society • Within the same person - there may exist two very different cultural menus • Bicultural individuals often describe experiencing two internalized cultures that take turns in guiding their thoughts and perceptions o Within any person, there is a dynamic ebb and flow to one's internalized culture It is not relied on continuously for interpretation and meaning - but instead • only a small subset of cultural knowledge • Frame switching - individuals alternate between these two internalized cultural mental sets o According to this model, bicultural individuals - when triggered by cues in the social environment, can switch between two interpretive frames rooted in their two different cultures Experimental Tasks and Stimuli • Well known experimental technique from cognitive psychology - priming o Occurs when exposure to a stimulus facilitates responses to a subsequent event o Initial exposure primes subsequent processing Developmental Studies • Progressive psychological changes that unfold across the entire life span as human beings age Cross Sectional Design • Cross sectional method - takes groups of people of different ages o Compares these age groups on psychological processes Confounded by cohort effects that result from comparing groups of persons who are at • different ages in one point in time • A cohort is defined as a group of individuals sharing a certain characteristic (age, year of high school graduation, locale, etc.
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