PSYCH 225: Chap 12- Final
21 Cards in this Set
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Quasi-experiments
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similar to true experiments, researchers select an independent variable and a dependent variable; then they study participants who are exposed to each level of the independent variable. but in Quasi, the experimenters do not have full experimental control.
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Nonequivalent control group design
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a quasi-experimetnal study that has at least one treatment group and one comparison group, but participants have not been randomly assigned to the two groups.
- different participants at each level of the independent variable.
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two examples of nonequivalent control group design
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- head start study
- staywell program
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Interrupted time-series design
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a quasi-experimental study that measures people repeatedly on a dependent variable before, during, and after the "interruption" caused by some event.
- ex. job burn out (vacation/interrupt)
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nonequivalent groups interrupted time-series design
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combines two of the previous designs (nonequivalent and interrupted time) Independent variable was studies both as a repeated-measures variable and as an independent-groups variable. And the researchers do not have experimental control over the manipulation of the independent variable or …
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Selection Effects/ Selection Threats
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-applies when the groups at the various levels of an independent variable contain different types of participants.
- Not clear whether it was the independent variable of the different types of participants in each group that led to a difference in the dependent variable between groups.
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Maturation Threat
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- Occurs when there is a pretest and posttest, a treatment group shows an improvement over time, but it is not clear whether the improvement was caused by the treatment or whether the group would have improved spontaneously, even w/o treatment.
- comparison groups help, and these effects…
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History Threat
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- Occurs when an external, historical event happens for everyone in a study at the same time as the treatment variable.
- It is unclear whether the outcome is caused by the treatment or by the common, external event.
- Comparison groups help
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selection-history threat
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because the history threat applies to only one group, not the other. Historical event systematically affects the subjects only in the treatment group or only in the comparison group- not in both.
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Regression to the mean
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- occurs when an extreme score is caused by a combination of random factors that are unlikely to happen in the same combination again, so the extreme score gets less extreme over time.
- Extreme score was a combination of random factors that did not repeat itself in the next game, so sco…
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Attrition Threat
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- applies when people drop out of a study for some systematic reason.
- Occurs mainly in designs with pretest and posttest.
- include in final analysis who completed entire study and who dropped out
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Testing and Instrumentation Threats
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- whenever researchers measure participants more than once, they need to be concerned about testing threats to internal validity.
- testing threat is a kind of order effect in which participants- whether students, animals, or anyone else- tends to change as a result of having been tested…
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Three effects related to human subjectivity
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- observer bias
- experimental demand
- placebo effect
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observer bias
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(threat to construct and internal) happens when the experimenters' expectations influence their interpretation of the results.
- blind experiments help this
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experimental demand
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when participants guess what the study is about and change their behavior in the expected direction.
- could they detect the study's purpose?!
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Placebo effect
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when participants improve, but only because they believe they are receiving an effective treatment.
- use comparison group with treatment vs. control vs. placebo
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small N design
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instead of gathering a little information from a larger sample, they obtain a lot of information from just a few cases.
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single N design
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when researchers restrict their study to only one animal or one person.
- chart in notes
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stable-baseline designs
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a study in which a researcher observes behavior for an extended baseline period before beginning a treatment or other intervention; if behavior during the baseline is stable, the researcher is more certain of the treatment's effectiveness.
- ex. ms. S and the memory test
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Multiple-baseline design
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researcher-practitioners stagger their introduction of an intervention across a variety of contexts, times, or situations.
- ex. 12 yr old with hair touching, then face, then grabbing. all a diff times
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reversal design
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a researcher also observers a problem behavior both with and without treatment. but in a reversal design, the practitioner takes the treatment away for a while (reversal) to see whether the problem behavior returns (reverses)
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PSYCH 225: Chap 12- Final