distinction between nonexperimental and quasi-experimental research design

research design makes little or no attempt to minimize threats

makes some attempt to minimize threats to internal validity and approaches the rigor of a true experiment

involve comparison of scores from different groups or different conditions. these two strategies use a nonmanipulated variable to define the groups or conditions being compared.

research study in which the different groups of participants are formed under circumstances that do not permit the researcher to control the assignment of individuals to groups.

simply compares preexisting groups. type of nonexperimental research design

Nonexperimental designs with Nonequivalent groups

uses preexisting groups, one of which serves in the treatment condition and the other in the control condition

one group of participants is given a treatment and then is measured after the treatment. the scores of the treated group are then compared with the scores from the nonequivalent group that hasn't received treatment

Quasi-Experimental Design with Nonequivalent Groups

one group is measured twice, once before and once after the treatment. the other group is measured at the same two times but does not receive any treatment

research study in which a series of observations is made over time for ONE group of participants.

threats to internal validity for Pre-Post design