Ch 10: More on Experiments Flashcards
attritition
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
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
demand characteristic
cues that lead participants to guess a study’s hypotheses or goals
double-blind placebo control study
a study that uses a treatment group and a placebo group and in which neither the research assistant nor the participants know who is in which group
floor effects
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
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 event that affects everyone or almost everyone in the group
instrumentation threat
a threat to internal validity that occurs when a measuring instrument changes over time from having been used before
maturation
a threat to internal validity that occurs when an observed change in an experimental group could have emerged more or less spontaneously over time
noise
the unsystematic variability among the members of a group in an experiment
null effect
a finding that an independent variable did not make a difference in the dependent variable- that there is no significant covariance between the two
one group, pretest/posttest design
a study 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
placebo effect
an effect that occurs when people receiving an experimental treatment experience a change only because they believe they are receiving a valid treatment
regression threat
a threat to internal validity related to regression toward the mean, by 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 the experimental treatment or intervention)
situation noise
irrelevant events, sounds, or distractions in the external situation that create unsystematic variability within groups in an experiment
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
