designs that do not control for many extraneous variables and provide weak evidence of cause and effect
administration of a postest to a single group of participants after they have been given an experimental treatment condition
allows no evidence of what the participants would have scored on the DV had they not received the treatment
no control group
Design in which a treatment condition is interjected between a pretest and postest of the dependent variable (can compare pretest and postest)
In most cases --> are unaware if the sources of the rival hypotheses affect the results
Can be used to provide some info
design in which the performance of an experimental group is compared with that of a nonequivalent control group at the posttest
can test whether or not the independent variable influenced the dependent variable
selection poses a problem
does not exclude possible selection effects from the treatment effect
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