PSYCH 225: Chap 10- Exam 3
24 Cards in this Set
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one-group/ posttest design
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a researcher recruits one group of participants, measures them on a pretest, exposes them to a treatment, intervention, or change and then measures them on a posttest.
- VERY BAD! threat to internal validity!!
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maturation
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change in behavior that emerges more or less spontaneously over time; has nothing to do with the manipulation.
- boys at camp got less rowdy because they got used to the camp.
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spontaneous remission
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(an example of maturation) when sxs of disorders get better for no known cause, with time.
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history threats
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threats to internal validity that occur when a "historical" or external event occurs to everyone in the treatment group at the same time as the treatment, so it is unclear whether the change in the experimental group caused by the treatment received or by the historical event.
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regression threat
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refers to a statistical concept called regression toward the mean: when a performance is extreme at Time 1, the next time that performance in measured (Time 2), it is likely to be less extreme- or closer to the typical, or average performance.
- ex. baseball game: 22-1
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attrition
(aka mortality)
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occurs when people drop out of the study before it ends. In a repeated-measures experiment or quasi-experiment, a threat to internal validity that occurs when a systematic type of participant drops out of a study before it ends.
-ex. maybe depressed women got better because 3 most depres…
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testing threat
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scored have changed over time just because participants have taken the test more than once.
- almost like order effect. people may become more practiced at taking the test or just may be tired/bored.
- prevent this by: abandoning pretest altogether or use alternative forms of the test A…
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instrumental threats (aka instrument decay)
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occur when a measuring instrument changes over time from having been used before.
- ex. observational research: over time the people who are coding behaviors might change their standards for judging the behavior- may become more strict or lenient depending on mood.
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observer bias
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occurs when researchers' expectations influence their interpretation of the results- or even influence the outcome of the study.
-threat to internal because alternative explanations, AND construct because it means that the ratings do not represent the true levels of the dependent variabl…
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demand characteristics
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problem when participants guess what thte study is supposed to be about and change their behavior in the expected direction.
-ex. depressed pts were getting therapy so they knew they were suppose to be getting less depressed so might have changed their self-reports in the expected dire…
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double-blind study
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- in which neither the participants nor the researchers who evaluate them know who is the treatment group and who is the comparison group.
- helps with demand characteristics--> observer bias too and better than a comparison group!
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placebo effect
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occurs when people receive a treatment and really improve- but only because they believe they are receiving a valid treatment.
- they improve simply because they believed they were receiving an effective treatment.
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double-blind placebo control studies
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neither the person treating the patients nor the patients themselves know whether they are in the real group or the placebo group.
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null effect
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a finding that an independent variable did not make a difference in the dependent variable- that there is no significant covariance between the two.
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weak manipulations
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- can obscure a true causal relationship
- important to ask how the researchers operationalized the independent variable, or ask about construct validity.
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insensitive measures
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- a null is sometimes found because the researchers have not used an operationalization of the dependent variable with enough sensitivity.
- instrument may not be sensitive enough to detect it.
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ceiling effects
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an experimental design problem in which independent variable groups score almost the same on a dependent variable, such that all scores fall at the HIGH end of their possible distribution.
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floor effect
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an experimental design problem in which independent variable groups score almost the same on a dependent variable, such that all scores fall at the LOW end of their possible distribution.
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confounds acting in reverse
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study may be designed in some way that a confound actually counteracts some true effect of an independent variable.
- the GRE prep course could be put under a lot of pressure to do well, while the pep talk group was not. This caused prep course to do worse than normal.
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noise
(aka error variance)
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the unsystematic variability among the members of a group in an experiment, may cause a null effect.
- 3 sources: measurement error, individual differences, and situation noise.
- difference between 2 group averages is the same; however, the variability within each group is much larger.
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measurement error
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term used for factors that can inflate or deflate a person's true score on a dependent measure.
- dependent variable score= subjects true score -/+ random error of measurement
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solutions to measurement error
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- Reliable, precise measurement
- measure more instances (larger population
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Solutions to individual differences
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1. change the design
- use within-grous design
- or matched-group design
2. add more participants
- especially when there's a lot of variability
- more people means one person will have less of an affect on the data
- then you can detect differences in between-groups as well!
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situation noise
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irrelevant events, sounds, or distractions in external situation that create unsystematic variability within groups is an experiment.
- third variable that could cause variability within groups and obscure true group differences.
- obscure true differences between groups
- control this…
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PSYCH 225: Chap 12- Final