Items selected at random from a population and used to test hypotheses about the population
Bias introduced to a sample when individuals can choose on their own whether to participate in the sample
A variable whose effect on the response variable cannot be separated from the effect of the explanatory variable on the response variable. Note: Usually confounded variables are lurking variables but only a few lurking variables are also confounded.
A technique whereby each participant is identical to one other participant in terms of a third variable