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scientific method  systematic method of obtaining and evaluating information relevant to a problem
hypothesis  testable statement about two or more variables and the relationship between them
null hypothesis  alternative to a primary hypothesis, stating that there is no relationship between the independent variable and the dependent variable
variable  measurable factor or characteristic that can vary within an individual, between individuals, or both
dependent variable  factor that an experimenter seeks to predict
independent variable  factor that is manipulated by an experimenter or used to predict the dependent variable
operationalization  specific manner in which variables in a study are measured or manipulated
case studies  in-depth analyses of individuals
generalizability  extent to which the results of a study generalize to, or inform us about, people other than those who were studied
correlational studies  method in which researchers assess only the relationship between two variables and do not manipulate one variable to determine its effects on another variable
continuous variable  factor that is measured along a continuum (such as 0-100) rather than falling into a discrete category (such as "diagnosed with depression")
group comparison study  study that compares two or more distinct groups on a variable of interest
cross-sectional  type of research examining people at one point in time but not following them over time
longitudinal  type of research evaluating the same group(s) of people for an extended period of time
correlation coefficient  statistic used to indicate the degree of relationship between two variables
statistical significance  likelihood that a study's results have occurred only by chance
third variable problem  possibility that variables not measured in a study are the real cause of the relationship between the variables measured in the study
sample  group of people taken from a population of interest to participate in a study
cohort effect  effect that occurs when people born in one historical period are at different risk for a disorder than are people born in another historical period
external validity  extent to which a study's results can be generalized to phenomena in real life
epidemiology  study of the frequency and distribution of a disorder, or a group of disorders, in a population
prevalence  proportion of the population who have a specific disorder at a given point or period in time
incidence  number of new cases of a specific disorder that develop during a specific period of time
risk factors  conditions or variables associated with a higher risk of having a disorder
experimental studies  studies in which the independent variables are directly manipulated and the effects on the dependent variable are examined
human laboratory study  experimental study involving human participants
internal validity  extent to which all factors that could extraneously affect a study's results are controlled within a laboratory study
control group  in an experimental study, group of subjects whose experience resembles that of the experimental group in all ways except that they do not receive the key manipulation
experimental group  in an experimental study, group of participants that receive the key manipulation
random assignment  assignment of participants in an experiment to groups based on a random process
demand characteristics  factors in an experiment that suggest to participants how the experimenter would like them to behave
double-blind experiment  study in which both the researchers and the participants are unaware of which experimental condition the participants are in, in order to prevent demand effects
therapy outcome studies  experimental studies that assess the effects of an intervention designed to reduce psychopathology in an experimental group, while performing no intervention or a different type of intervention on another group
wait list control group  in a therapy outcome study, group of people that functions as a control group while an experimental group receives an intervention and then receives the intervention itself after a waiting period
placebo control group  in a therapy outcome study, group of people whose treatment is an inactive substance (to compare with the effects of a drug) or a nontheory-based therapy providing social support (to compare with the effects of psychotherapy)
efficacy  in therapy outcome research, how well a therapy works in highly controlled settings with a narrowly defined group of people
effectiveness  in therapy outcome research, how well a therapy works in real-world settings
single-case experimental design  experimental design in which an individual or a small number of individuals are studied intensively; the individual is put through some sort of manipulation or intervention, and his or her behavior is examined before and after this manipulation to determine the effects
ABAB (reversal) design  type of experimental design in which an intervention is introduced, withdrawn, and then reinstated, and the behavior of a participant is examined on and off the treatment
multiple baseline design  type of study in which an intervention is given to the same individual but begun in different settings or is given to different individuals but at different points in time and in which the effects of the intervention are systematically observed
animal studies  studies that attempt to test theories of psychopathology using animals
family history study  study of the heritability of a disorder involving identifying people with the disorder and people without the disorder and then determining the disorder's frequency within each person's family
monozygotic (MZ) twins  twins who share 100 percent of their genes because they developed from a single fertilized egg
dizygotic (DZ) twins  twins who average only 50 percent of their genes in common because they developed from two separate fertilized eggs
twin studies  studies of the heritability of a disorder by comparing concordance rates between monozygotic and dizygotic twins
concordance rate  probability that both twins will develop a disorder if one twin has the disorder.
adoption study  study of the heritability of a disorder by finding adopted people with a disorder and then determining the prevalence of the disorder among their biological and adoptive relatives, in order to separate out contributing genetic and environmental factors
molecular genetic studies  studies of the structure and function of genes that help in understanding how genetic mutations can lead to disease
association studies  genetic studies in which researchers identify physical disorders associated with a target psychological disorder for which genetic abnormalities or markers are known; the DNA of individuals with the psychological disorder and their first-degree relatives is then examined to determine if they also have this genetic marker (one form of molecular genetic studies)
linkage analysis  genetic study that looks for associations between psychological disorders and physical disorders for which genetic causes are known
meta-analysis  statistical technique for summarizing results across several studies







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