Experiments and Quasi-Experiments (Schwab, 2005) Flashcards
Threats to internal validity
Characteristics of research studies that make a causal claim that an independent variable leads to a dependent variable vulnerable to alternative.explanations.
Between-cases design
Design that uses two or more cases or groups of cases; each case or group experiences different levels of an independent variable. Effect of an independent
variable is assessed by comparing dependent variable scores across the cases or groups of cases.
Cross-sectional design
Design in which the independent and dependent variables are measured only once. The relationship between the variables is taken as evidence of the influence of X on Y.
Within-cases design
Design that uses one case or one group of cases. Effect of an independent variable is assessed by measuring the dependent variable before and after a change in the level of the independent variable.
Longitudinal design
Design in which the dependent (and perhaps, independent) variable is measured more than once.
Demand characteristics
Characteristics of a research study that motivate participants’ expectations about what is investigated; a threat to internal validity.
Expectancy effects
A nuisance variable that influences the dependent variable because a researcher treats some cases differently than others based on assumptions made about expected research results; a threat to internal validity.
Selection
A threat to internal validity when there are preexisting differences between groups experiencing different levels of an independent variable. These differences may account for differences observed on the dependent variable.
Omitted variable
An independent variable that operates in the causal system studied but that is not included in the model studied. Serves as a threat to internal validity in the same way selection is a threat.
Intragoup history
An exogenous event(s) that has an impact on a group of cases that experience one level of an independent variable differently than the event influences groups
experiencing other levels of the independent variable; a threat to internal validity.
Treatment contamination
Occurs when a level of an independent variable assigned to one group of participants is communicated to another; a threat to internal validity.
History
An exogenous event that occurs between measurements of the dependent variable; a threat to internal validity in longitudinal designs.
Maturation
Changes in cases between measurements of the dependent variable; a threat to internal validity in longitudinal designs.
Mortality
Occurs when some cases leave between measurements of the dependent variable; a threat to internal validity in longitudinal designs.
Testing
A threat to internal validity in longitudinal designs when the initial measurement of a dependent variable influences participants’ responses to the dependent variable on a subsequent measurement of it.
