Chapter 11 Flashcards
alternative explanation
the existence of any systematic difference between groups other than the experimental variables that threaten internal validity
experimental variables
properties an experimenter can manipulate or expose people to
independent variable
the variable we believe to have a causal influence on our outcome variables
counterbalancing
varying the order of experimental conditions across participants in a repeated measures design // helps to assure internal validity + controls for possible contamination
failure of randomization
for any given study, it is possible that particular kinds of participants will not be evenly distributed across experimental conditions
random assignment
a way of assigning participants to the levels of the independent variable so that the groups do not differ as the study begins
randomized experiment
a research design in which individuals are randomly assigned to various levels of the independent variable
repeated measures design
rather than some participants being in one condition and some in the other, all participants are in both conditions
artifacts
an unintended effect on the dependent variable that is caused by some feature of the experimental setting other than the independent variable
construct validity
making sure that our variables capture the construct we wish to measure
differential mortality
when mortality rates are different for the various experimental groups // posing threat to internal validity
factorial design
design containing every possible combination of two or more independent variables
history
any event that is unrelated to the independent variable and yet could affect the dependent variable
instrumentation
any change that occurs over time in measurement procedures or devices
interaction effect
when the effect of one variable differs depending on the level of the other variable
main effect
the effect of one independent variable, ignoring the others
manipulated variable
when researchers create rather than measure levels of an independent variable
manipulation check
a measure of the independent variable construct after they have measured it
maturation
any naturally occurring process within persons that could cause a change in their behavior (i.e. fatigue, boredom, growth)
mortality
any attrition (gradual loss) of participants from a study
pretests
an additional set of tests or observations of the dependent variable before the experimental treatment
selection
any pre-existing differences between individuals in the different experimental conditions that can influence the dependent variable
selection by maturation
when there are differences between individuals in the treatment groups that produce changes in the groups at different rates
