RM Final

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  1. one group, pretest/post test design
    an experiment in which 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.
  2. maturation threat
    a threat to internal validity that occurs when an observed change in an experimental group could have emerged more or less spontaneously over time.
  3. history threat
    a threat to internal validity that occurs when it is unclear whether a change in the treatment group is caused by the treatment or by a historical factor or event that affects everyone or almost everyone in the group.
  4. regression threat
    a threat to internal validity related to regression to the mean, a phenomenon in which any extreme finding is likely to be closer to its own typical, or mean, level the next time it is measured (with or without experimental treatment or intervention).
  5. attrition threat
    in a repeated measures design or quasi-experiment, a threat to internal validity that occurs when a systematic type of participant drops out of a study before it ends.
  6. testing threat
    in a repeated-measures experiment or quasi-experiment, a kind of order effect in which scores change over time just because participants have taken the test more than once; includes practice effects and fatigue effects.
  7. instrumentation threat
    a threat to internal validity that occurs when a measuring instrument changes over time from having been used before.
  8. selection-history threat
    a threat to internal validity in which a historical or seasonal event systematically affects only the subjects in the treatment group or only those in the comparison group, not both.
  9. selection-attrition threat
    a threat to internal validity in which members are likely to drop out of either the treatment group or the comparison group, not both.
  10. observer bias
    a bias that occurs when observers' expectations influence their interpretation of the participants' behaviors or the outcome of the study.
  11. demand characteristic
    a threat to internal validity that occurs when some cue leads participants to guess a study's hypotheses or goals.
  12. double-blind study
    a study in which neither the participants nor the researchers who evaluate them know who is in the treatment group and who is in the comparison group.
  13. masked design
    a study design in which the observers are unaware of the experimental conditions to which participants have been assigned.
  14. placebo effect
    a response or effect that occurs when people receiving an experimental treatment experience a change only because they believe they are receiving a valid treatment.
  15. double-blind placebo control study
    a study that uses a treatment group and a placebo group and in which neither the research staff nor the participants know who is in which group.
  16. null effect
    a finding that an independent variable did not make a difference in the dependent variable; there is no significant covariance between the two.
  17. ceiling effect
    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.
  18. floor effect
    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.
  19. manipulation check
    in an experiment, an extra dependent variable researchers can include to determine how well an experimental manipulation worked.
  20. noise
    the unsystematic variability among the members of a group in an experiment.
  21. measurement error
    the degree tow which the recorded measure for a participant on some variable differs from the true value of the variable for that participant. measurement errors may be random, if over a sample they both inflate or deflate true scores, or they may be systematic, in which case they may results in biased measurement.
  22. situation noise
    unrelated events or distractions in the external environment that create unsystematic variability within groups in an experiment.
  23. power
    the likelihood that a study will show a statistically significant result when some effect is truly present in the population; the probability of not making a type II error.
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RM Final
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RM final
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