Chapter 6: Causation and Experimental Design Flashcards
Causal effect
The finding that change in one variable leads to change in another variable (other things being equal.)
Ex. Individuals arrested for domestic assault tend to commit fewer subsequent assaults than similar individuals who are accused in the same circumstances but are not arrested
Ceteris paribus
Latin phrase meaning “other things being equal.”
Association
A criterion for establishing a causal relationship between two variables. Variation in one variable is empirically related to variation in another variable
Time order
A criterion for establishing a causal relationship between two variables. The variation in the presumed cause (the independent variable) must occur before the variation in the presumed effect (the dependent variable).
Nonspuriousness
A criterion for establishing a causal relation between two variables; when a relationship between two variables is not caused by a variation in a third variable
Spurious
Nature of a presumed relationship between two variables that actually results from variation in a third variable
Mechanism
A discernible process that creates a causal connection between two variables
Context
The larger set of interrelated circumstances in which a particular outcome should be understood
True experiment
Experiment in which subjects are assigned randomly to an experimental group that receives a treatment or other manipulation of the independent variable an a comparison group that does not receive the treatment or receives some other manipulation. Outcomes are measured in a posttest.
Comparison group
In an experiment, groups that have been exposed to different treatments or values of the independent variable (e.g., a control group an an experimental group).
Experimental group
In an experiment, the group of subjects that receives the treatment or experimental manipulation.
Control group
A comparison group that receives no treatment
R, O, and X
R = random assignment O = Observation (prestest [O1] or posttest [O2]) X = Experimental treatment
Posttest
In experimental research, the measurement of an outcome (dependent) variable after an experimental intervention or after a presumed independent variable has changed for some other reason. The posttest is exactly the same “test” as the pretest, but it is administered at a different time.
Pretest
In experimental research, the measurement of an outcome (dependent) variable before an experimental intervention or change in a presumed independent variable for some other reason. The pretest is exactly the same “test” as the posttest, but it is administered at a different time
Random assignment (randomization)
A procedure by which each experimental subject is placed in a group randomly
Matching
A procedure for equating the characteristics of individuals in different comparison groups in an experiment. Matching can be done on either an individual or an aggregate basis. For individual matching, individuals who are similar in key characteristics are paired before assignment, and then the two members of each pair are assigned to the two groups. For aggregate matching, groups chosen for comparison are similar in distribution of key characteristics.
Quasi-experimental design
A research design in which there is a comparison group that is comparable to the experimental group in critical ways but subjects are not randomly assigned to the comparison and experimental groups
Nonequivalent control group design
A quasi-experimental design in which there are experimental and comparison groups that are designated before the treatment occurs but are not created by random assignment
Before-and-after design
A quasi-experimental design consisting of several before-and-after treatment comparisons involving the same variables but no comparison group
Ex post facto control group design
A nonexperimental design in which comparison groups are selected after the treatment, program, or other variation in the independent variable has occured
Multiple group before-and-after design
A type of quasi-experimental design in which several before-and-after comparisons are made involving the same independent and dependent variables but different groups
Repeated measures panel design
A quasi-experimental design consisting of several pretest and posttest observations of the same group
Time series design
A quasi-experimental design consisting of many pretest and posttest observations of the same group
11 Threats to Internal Validity
- Selection
- Mortality
- Instrument Decay
- Testing
- Maturation
- Regression
- History
- Contamination
- Experimenter Expectation
- Placebo Effect
- Hawthorne Effect
Selection Bias
A source of internal (causal) invalidity that occurs when characteristics of experimental and comparison group subjects differ in any way that influences the outcome
Differential attrition (mortality)
A problem that occurs in experiments when comparison groups become different because subjects in one group are more likely to drop out for various reasons compared with subjects in the other group(s).
Instrument Decay
The deterioration over time of a measurement instrument, resulting in increasingly inaccurate results
Endogenous change
A source of causal invalidity that occurs when natural developments or changes in the subjects (independent of the experimental treatment itself) account for some of all the observed change from the pretest to the posttest.
Regression effect
A source of causal invalidity that occurs when subjects chosen because of their extreme scores on a dependent variable become less extreme on a posttest as a result of mathematically necessity, rather than the treatment.
History effect (affect of external events)
Events external to the study that influences posttest scores, resulting in causal invalidity
Contamination
A source of causal invalidity that occurs when either the experimental or the comparison group is aware of the other group and is influenced in the posttest as a result
Compensatory rivalry (John Henry effect)
A type of contamination in experiment and quasi-experimental designs that occurs when control group members are aware that they are being denied the treatment and modify their efforts by way of compensation
Demoralization
A type of contamination in experimental and quasi-experimental designs that occurs when control group members feel that they have been left out of some valuable treatment, performing worse than expected as a result
Treatment misidentification
A problem that occurs in an experiment when not the treatment itself, but rather some unknown or unidentified intervening process, is causing the outcome
Expectancies of experiment staff (self-fulfilling prophecy)
A source of treatment misidentification in experiments and quasi-experiments that occurs when change among experimental subjects results from the positive expectancies of the staff who are delivering the treatment, rather than to the treatment itself.
Double-blind procedure
An experimental method in which neither the subjects nor the staff delivering experimental treatments know which subjects are getting the treatment
Placebo effect
A source of treatment misidentification that can occur when subjects receive a treatment that they consider likely to be beneficial and improve as a result of that expectation rather than the treatment itself.
Hawthorne effect
A type of contamination in experimental and quasi-experimental designs that occurs when members of the treatment group change relative to the dependent variable because their participation in the study makes them feel special
Process analysis
A research design in which periodic measures are taken to determine whether a treatment is being delivered as planned, usually in a field experiment
Field experiment
An experimental study conducted in a real-world setting
Solomon Four-Group Design Testing the Interaction of Pretesting and Treatment
R O1 X O2
R 01 O2
R X O2
R O2
R = random assignment O = observation (pretest or posttest) X = experimental treatment
Distribution of benefits
An ethical issue about how much researchers can influence the benefits subjects receive as part of the treatment being studied in a field experiment
