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Chapter 8

PSYB01 Chapter 8 Notes

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David Nussbaum

RESEARCH METHODS IN PSYCHOLOGY Chapter 8: Quasiexperimental and Non-experimental Designs Quasiexperimental Design  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  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  In studies of the effects of a natural treatment on a dependent variable, exposure and non- exposure would form two levels of the independent variable  Subject variables and natural treatments belong to a distinct class of independent variables that many behavioural researchers term “quasi-independent”  A quasiexperiment is one that investigates the effects of a quasi-independent variable on a dependent variable o Resembles a true experiment except for the degree to which an experimenter can directly control and manipulate one or more of the independent variables o The label quasi gives a negative connotation and often implies a lower status of second-class citizenship for a quasiexperiment in relation to a true experiment  Quasiexperiments offer a fertile research design for investigating some of the most important and creative questions in psychology  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 have pretest and post-test but not comparison group. The participants are exposed to the treatment serve, at an earlier time, as their own controls o Interrupted-time-series design, multiple-group before-and-after design, repeated- measures-panel design Natural Treatments as Quasi-Independent Variables  Suppose we wanted to study the psychological effects of 9/11. We select 9/11 as our quasi-independent variable because we cannot directly control or manipulate via random assignment exposure to 9/11 since it is considered a natural treatment o Researchers can only provide an “after-the-fact” or ex post facto analysis of its effect on a particular dependent variable such as memory, suicide rates, or grades Subject Variables as Quasi-Independent Variables  Suppose we want to study 9/11 but this time we are interested in gender differences in response to 9/11, we now have two quasi-independent variables, one which is a natural treatment, 9/11, and a subject variable, gender  In many instances, research designs incorporate both a manipulated variable along with a manipulated independent variable o For example, social attention and non-social attention as measured by speeded target detection in persons with schizophrenia and in a control group of healthy volunteers were compared. Diagnosis of schizophrenia is the quasi-independent RESEARCH METHODS IN PSYCHOLOGY variable forming the experimental group and the absence of schizophrenia formed the control group o We manipulated within subjects two forms of attention, social and non-social, and presented these two experimental tasks in a counterbalanced order  The schizophrenia study is an example of a quasiexperiment that used a mixed-factorial design because it combines both between- and within-subjects factor Nonequivalent-Control-Group Designs  Random assignment provides us with the best chance of ensuring the groups would be equivalent at the beginning of the experiment before the treatment or the manipulation of the independent variable  If groups formed by random assignment subsequently differed on the dependent variable, hen such difference, in principle, would be attributable to treatment or the independent variable  In quasiexperiments, the control and experimental groups are not formed by random assignment, rather the groups are selected on the basis of pre-existing, immutable subject characteristics or exposure to some kind of natural treatment o The control group cannot be considered equivalent to the experimental group o Pre-existing differences cannot be equalized by random assignment  Nonequivalent-control-group designs have experimental and control groups that have been predetermined or predesignated by existing subject characteristic or an already- occurred treatment  Consider a study by Ruth Wageman (1995) that investigates how the organization of work tasks and rewards affected work team functioning. Research question was whether it was preferable to organize work and work rewards in a way that stressed either interdependence or individual autonomy o Three groups were created that differed considerably and research design could not disentangle the effects of the intervention itself from the effects of the district manager, who not only implemented the strategy but also decided which one to use o Cofounds clearly limit the extent to which we can draw internally valid conclusions from the study  Quasiexperimental studies with nonequivalent control or comparison of groups often receive high marks for their external validity in general, and their ecological validity in particular o Often high in generalizability and high in realism Matching  In individuals matching, individual cases in the treatment group are matched with similar individuals in the control group o This may create a control group that is very similar to the experimental group  In most situations when random assignment is not possible, the second method of matching makes more sense: identifying a comparison group that matches the treatment group in the aggregate rather than trying to match individual cases, referred to as aggregate matching RESEARCH METHODS IN PSYCHOLOGY  A researcher matches on a variable that is highly related to the dependent variable. Oftentimes, a researcher can collect pretest measures and then match participants either individually or in the aggregate on pretest scores  Regression artifact can occur anytime a pretest measure is used for matching o Suppose you calculated the pretest reading comprehension score for two student groups. There are 20 students in each class, so we would sum all of their pretest scores, divided by 20, to get the mean or average for each group. We could then compare students with extreme pretest scores with post-test scores o What often occurs is that people who received extreme scores on a test of ability when retested on that same ability earn scores that are closer to the mean of their group than were their original score. This is known as regression to the mean  Regression to the mean may be a confounding factor for interpreting results of studies that match groups on pretest measures Before-and-After Designs  The common feature of this design is the absence of a comparison group. Because all cases are exposed to the experimental treatment, the basis for comparison is provided by comparing the pre-treatment to the post-test measures  These designs are useful for studies of interventions that are experienced by virtually every case in some population, such as total coverage programs like Social Security  The simplest type of before-and-after design is the fixed-sample panel design with one pretest and one post-test  The interrupted-time-series design is often used to examine observations before and after a naturally occurring treatment o In the simplest time series design, there is a single experimental group for which we have obtained multiple observations before and after a naturally occurring treatment o Such a design might be used to examine the effects of a public policy change on a particular behaviour, such as the influence of changing the age of legal drinking on car accidents in young drivers  John Gibbons investigated the effect of public health warnings about the safety of antidepressant drugs issued by U.S. and European regulators in 2003 and 2004. The warnings discouraged the use of antidepressants in children and adolescents. o The researchers wanted to know whether the policies had inadvertently led to untreated depression in the young that in turn contributed to their jump in suicide rates o Naturally occurring treatment is the policy change discouraging the use of antidepressants o The researchers cited several prior studies, all of which should have told the regulators that their warnings to discourage antidepressant use lacked empirical support and that it could indeed be harmful to the mental health and well-being of depressed children and adolescents o The researchers correlated annual rates of antidepressant prescriptions and suicide for children and teens and interpreted their findings as showing that regulatory RESEARCH METHODS IN PSYCHOLOGY policies discouraging the use of antidepressants in children and adolescents may have inadvertently increased suicide rates for these groups o Remarkable ecological validity as they suggested antidepressants may help reduce suicide rates o This study may be viewed as a quasiexperiment of the effects of a natural treatment (public health warnings|) on a dependent variable or outcome measure (suicide rates)  David P. Phillips study of the effect of TV soap-opera suicides on the number of actual suicides in U.S. illustrates a powerful 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 o Researchers had 13 different before-and-after studies, one for each suicide story. In 12 of these 13 comparisons, deaths due to suicide increased from the week before each soap-opera suicide to the week after  Another type of before-and-after design involves pretest and post-test observations of the same group. These may be repeated-measures panel designs and time series designs, such as the interrupted-time-series study of Gibbons and colleagues  Repeated-measures panel designs 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  In a time series design, you compare the trend in the dependent up to the date of the intervention or event whose effect is being studied and the trend in the dependent variable after the intervention o A substantial disparity between the pre-intervention trend and the post- intervention or event had an impact o Particularly useful for studies of impact of new laws or social programs that affect everyone and that are readily assessed by some ongoing measurement  Paul A. Nakonezny and colleagues used a time series design to identify the impact of the Oklahoma City terrorist bombing in April 1995 on the divorce rate in Oklahoma. They hypothesized that people would be more likely to feel a need for support in the aftermath of such a terrifying event and thus be less likely to divorce o First calculated the average rate of change in divorce rates in Oklahoma’s 77 counties in the 10 years prior to the bombing and then projected these rates forward to the 5 years after the bombing o They found that the actual divorce rate in the first years after the bombing was lower than the pre-bombing trend would have predicted, but this effect was diminished to nothing by the year 2000 A Quasiexperiment of Memories of 9/11  Sharot, Martorella, Delagado and Phelps recruited participants who had been in the vicinity of the World Trade Center on the morning of 9/11 when the terrorist attacks occurred RESEARCH METHODS IN PSYCHOLOGY  The researchers employed functional magnetic resonance imaging (fMRI), a widely used technique that records the brain at work, in real time, while and individual performs a task o The fMRI technology can be combined with various behavioral exercises, and these performance tasks can entail highly controlled experiments of various aspects of thinking, remembering, feeling, and concentration o Uses a blood oxygen dependence level signal to measure brain activation while participants perform various tasks o By examining brain patterns, researchers can identify various neural networks that underlie different kinds of performance, whether involving memory, attention, perception, or virtually any other kind of information processing Experimental Stimuli and Task  In the Sharot study, for the experimental task, participants viewed words that numerous prior studies have shown to be effective cues for memory  Researchers wanted to see if specific words (morning, New York City, lunch, evening and weather) would cue different memories depending on the experimental condition in which they were presented. There were two experimental conditions: September 2001 and summer 2001  The fMRI recorded brain responses to these memories in response to the word cues. Later, outside the fMRI scanner, participants again saw the same word cues paired either with September 2001 or summer 2001. But this time, participants rated each word-cued memory on 6 characteristics: (1) arousal, (2) vividness, (3) reliving, (4) remember/know, (5) confidence, and (6) valence  Sharot and colleagues used memory as a within-subjects variable with two levels: summer 2001 and September 2001  All participants received the same word cues, presented at a time for both conditions. As one of the dependent measures, the researchers recorded brain activity while participants viewed cue words in both conditions  In addition, the other dependent measure was ratings of the word cues on the six characteristics that the participants completed outside the fMRI Ex Post Facto Variable and Comparison Groups  Sharot and colleagues found that not only did the 9/11 memories have higher ratings than did summer 2001 on each of these attributes, but individuals differed considerably in their ratings  The researcher examined surveys that all participants had completed, among the information surveyed included distance of proximity to the WTC on the day that terrorists attacked o Wanted to know whether being closer to the WTC on that day influenced memory and brain responses for 9/11  Subsequently divided participants into two groups, those who were closer to the WTC, defined as a mean 2.08 miles, labeled as the Downtown group, and those farther away from the WTC, defined as a mean distance of 4.53 miles, labeled as Midtown group RESEARCH METHODS IN PSYCHOLOGY o Example of researchers creating comparison groups ex post facto, meaning, in this instance, after the fMRI and word-rating data had been collected o Created a new subject variable based on their participants’ ratings of their memories on the six characteristics, a single score labeled “recollective experience enhancement”  This quasiexperimental approach is very different from a factorial experiment in which groups are formed by random assignment and variables are defined conceptually and operationally a priori Correlational Relationships  Quasiexperiments lack design features that improve internal validity, this lessening confidence in causal conditions  The degree and direction of a relationship between two variables can be tested with a single statistic known as the correlation coefficient (r) which varies from -1.00 through 0.00 to +1.00 o The number value indicates the strength of the relationship between the two variables – a larger number indicates a stronger relationship o The sign, whether positive or negative, indicates the direction of the relationship – positive indicates that as one variable increases, so too does the other. A negative correlation indicates that as one variable increases, the other decreases  Sharot et al. found a statistically significant, negative correlation between WTC distance and 9/11 memories (r = -0.67) o Participants who were closer had higher ratings  Researchers often use scatter diagrams to graph correlations  Participants who were downtown and closest to the WTC on that day showed a different pattern of brain activation from participants who were farther away o The Downtown group showed the greatest activation of the amygdala, which is adjacent to the hippocampus that is known to be crucial in remembering, thus played an important role in providing the emotional tone and intensity for memories in those participants o The fMRI data showed the intense activation of the amygdala during retrieval of 9/11 memories relative to summer memories in research participants  The effect of the group (Midtown vs. Downtown) depended upon whether the cue words came in the September 2001 condition or in the summer 2001 condition o There are two independent variables, group and memory conditioning. Each has two levels: group (Midtown vs. Downtown) and memory conditioning (September 2001 vs. Summer
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