2confoundingObscuringVariables Flashcards
Maturation
A threat to internal validity that occurs when an observed change in an exp gp g erimental group could have emerged more or less spontaneously over time. E.g., Spontaneous remission
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. The event must affect the group systematically, not unsystematically
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). An unusually good performance or outcome is likely to regress downward; an unusually bad performance or outcome is likely to regress upward.When the people measured in a pretest condition are extreme on the dependent variable, regression is likely to be a threat to internal validity. If the comparison group and the experimental group are equally extreme at pretest, the researchers can account for any regression effects in their results
Attrition
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. Sometimes called Sometimes called mortality “mortality”
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.
Instrumentation threat
A threat to internal validity that occurs when a measuring instrument changes over time from having been used before. Also called instrument decay Also called instrument decay.
Observer Bias
A bias that occurs when observers’ expectations influence their interpretation of the subjects interpretation of the subjects behaviors or the ’ behaviors or the outcome of the study. Can be a threat to internal validity in almost any study in which there is a behavioral dependent variable. Observer bias can threaten internal and construct validity in an experiment.
Demand characteristics
Cues that lead participants to guess a study’s hypotheses or goals.
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. Placebo group: A control group that is exposed to an inert treatment (e.g., a sugar pill)
Double-blind placebo control study:
A study that uses d l b a treatment group and a placebo groupand in which neither the research assistant nor th i i k h i i hi h e participants know who is in which group
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.
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. Asking math questions too easy, everyone gets them right
Floor effect
An experimental design problem in which independent variable groups score al t th d d t i bl h lmost the same on a dependent variable, such that all scores fall at the low end of their possible distributionasking math problems too hard, nobody gets them right
Reverse-Confound
confounds can apply to null effects too apply to null effects, too. A study might be designed in such a way that a conf d t ll t t t ff t found actually counteracts some true effect of an independent variable.
