Chapter 9: Quantitative Research Design

attrition
the loss of participants over the course of a study, which can create bias by changing the composition of the sample initially drawn
baseline data
data collected before an intervention, including pretreatment measures of outcomes
between-subjects design
a research design in which there are separate groups of people being compared (e.g., smokers and non-smokers)
blinding
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
case-control design
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)
comparison group
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
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
correlational research
research that explores the interrelationships among variables of interest, without researcher intervention
crossover design
an experimental design in which one group of subjects is exposed to more than one condition or treatment, in random order
cross-sectional design
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
counterfactual
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
experiment
a study in which the researcher controls (manipulates) the independent variable and randomly assigns subjects to different conditions
external validity
the degree to which study results can be generalized to settings or samples other than the one studied
factorial design
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
history threat
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
homogeneity
(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)
internal validity
the degree to which it can be inferred that the experimental treatment (independent variable), rather than uncontrolled, confounding factors, caused the observed effects
intervention fidelity
the extent to which the implementation of a treatment is faithful to its plan
longitudinal design
a study designed to collect data at more than one point in time in contrast to a cross-sectional study
masking
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
manipulation
the introduction of an intervention or treatment in an experimental or quasi-experimental study to assess its impact on the dependent variable
matching
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
maturation threat
a threat to internal validity of a study that results when changes to the outcome (dependent) variable result from the passage of time
nonequivalent control group design
a quasi-experimental design involving a comparison group that was not created through random assignment
nonexperimental study
studies in which the researcher collects data without introducing an intervention; also called observational research
posttest-only design
an experimental design in which data are collected from subjects only after the intervention has been introduced; also called an after-only design
pretest-posttest design
an experimental design in which data are collected from research subjects both before and after introducing an intervention; also called a before-after design
prospective design
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
quasi-experiment
an experiment that involves an intervention but lacks randomization, the signature of a true experiment; also called controlled trials without randomization
random assignment (randomization)
the assignment of participants to treatment conditions in a random manner (i.e., in a manner determined by chance alone); also called randomization
retrospective design
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)
selection threat (self-selection)
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
time-series design
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
within-subjects design
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)