Chapter 11: Confounding and obscuring variables Flashcards
one-group pretest/posttest designs
- “the really bad experiment”
an experiment in which a researcher recruits one group of participants and measures them on a pretest, exposes them to treatment, intervention, or change, and then measures them on a posttest
maturation threat
a threat to internal validity that occurs when an observed change in an experimental group could have emerged spontaneously over time
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 itself or by an external or historical factor that affects most members of the group
regression threat
an internal validity threat related to regression to the mean:
- when a group mean is unusually extreme at time 1, the next time the group is measured (time 2), the mean is less likely to be extreme and instead be closer to its typical or average performance
attrition threat
in a pretest/posttest, repeated measures design or quasi-experimental design, a threat to internal validity that occurs when a systematic type of participant drops out of the study before it ends
testing threat
in a repeated measures experiment or quasi-experiment, a kind of order effect in which scores change over time because participants have taken the test (dependent measure) more than once
instrumentation threat
a threat to internal validity that occurs when a measuring instrument changes over time
selection-history threats
a threat to internal validity in which a historical or seasonal event systematically affects only the participants in the treatment group or only those in the systematic group
selection-attrition threat
a threat to internal validity in which participants are likely to drop out of either the treatment group or the comparison group
double-blind study
neither the participants nor the researchers know who is in the treatment group and who is in the comparison group
masked (blind) design
observers are unaware of the experimental conditions to which participants have been assigned to
null effect
a finding that the independent variable did not make a difference in the dependent variable and there is no significant covariance between the 2
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 the distribution
floor effect
independent variable groups score almost the same on a dependent variable, such that all scores fall at the low end of the distribution
measurement error
the degree to which the recorded measure for a participant on some variable differs from the true value of the variable for that participant
