Chapter 9: Quantitative Research Design
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attrition
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the loss of participants over the course of a study, which can create bias by changing the composition of the sample initially drawn
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baseline data
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data collected before an intervention, including pretreatment measures of outcomes
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between-subjects design
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a research design in which there are separate groups of people being compared (e.g., smokers and non-smokers)
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blinding
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the process of preventing those involved in a study (participants, intervention agents, or data collectors) from having information that could lead to a bias (e.g., knowledge of which treatment group a participant is in); also called masking
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case-control design
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a nonexperimental research design involving the comparison of \"cases\" (i.e., people with the condition under scrutiny, such as having a fall) and matched controls (similar people without the condition)
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comparison group
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a group of study participants whose scores on a dependent variable are used to evaluate the outcomes of the group of primary interest (e.g., nonsmokers as a comparison group for smokers); term often used in lieu of control group when the study design is not a true experiment
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control group
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subjects in an experiment who do not receive the experimental treatment and whose performance provides a baseline against which the effects of the treatment can be measured
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correlational research
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research that explores the interrelationships among variables of interest, without researcher intervention
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crossover design
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an experimental design in which one group of subjects is exposed to more than one condition or treatment, in random order
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cross-sectional design
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a study design in which data are collected at one point in time; sometimes used to infer change over time when data are collected form different age or developmental groups
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counterfactual
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the condition or group used as a basis of comparison in a study, embodying what would have happened to the same people exposed to a causal factor if they simultaneously were not exposed to the causal factor
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experiment
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a study in which the researcher controls (manipulates) the independent variable and randomly assigns subjects to different conditions
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external validity
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the degree to which study results can be generalized to settings or samples other than the one studied
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factorial design
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an experimental design in which two or more independent variables are simultaneously manipulated, permitting a separate analysis of the main effects of the independent variables and their interaction
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history threat
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the occurrence of events external to an intervention but concurrent with it, which can affect the dependent variable and threaten the study's internal validity
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homogeneity
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(1) in terms of the reliability of an instrument, the degree to which its subparts are internally consistent (i.e., are measuring the same critical attribute); (2) more generally, the degree to which objects are similar (i.e., characterized by low variability)
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internal validity
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the degree to which it can be inferred that the experimental treatment (independent variable), rather than uncontrolled, confounding factors, caused the observed effects
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intervention fidelity
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the extent to which the implementation of a treatment is faithful to its plan
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longitudinal design
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a study designed to collect data at more than one point in time in contrast to a cross-sectional study
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masking
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the process of preventing those involved in a study (participants, intervention agents, or data collectors) from having information that could lead to a bias (e.g., knowledge of which treatment group a participant is in); also called blinding
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manipulation
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the introduction of an intervention or treatment in an experimental or quasi-experimental study to assess its impact on the dependent variable
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matching
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the pairing of subjects in one group with those in a comparison group based on their similarity on one or more dimension, to enhance group comparability
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maturation threat
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a threat to internal validity of a study that results when changes to the outcome (dependent) variable result from the passage of time
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nonequivalent control group design
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a quasi-experimental design involving a comparison group that was not created through random assignment
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nonexperimental study
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studies in which the researcher collects data without introducing an intervention; also called observational research
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posttest-only design
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an experimental design in which data are collected from subjects only after the intervention has been introduced; also called an after-only design
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pretest-posttest design
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an experimental design in which data are collected from research subjects both before and after introducing an intervention; also called a before-after design
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prospective design
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a study design that begins by measuring a presumed cause (e.g., cigarette smoking) and then goes forward in time to measure presumed effects (e.g., lung cancer); also called cohort design
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quasi-experiment
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an experiment that involves an intervention but lacks randomization, the signature of a true experiment; also called controlled trials without randomization
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random assignment (randomization)
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the assignment of participants to treatment conditions in a random manner (i.e., in a manner determined by chance alone); also called randomization
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retrospective design
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a study design that begins with the manifestation of the dependent variable in the present (e.g., lung cancer), followed by a search for a presumed cause occurring in the past (e.g., cigarette smoking)
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selection threat (self-selection)
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a threat to a study's internal validity resulting from preexisitng differences between groups under study; the differences affect the dependent variable in ways extraneous to the effect of the independent variable
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time-series design
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a quasi-experimental design involving the collection of data over an extended time period, with multiple data collection points both before and after an intervention
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within-subjects design
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a research design in which a single group of subjects is compared under different conditions or at different points in time (e.g., before and after surgery)
