Why is the control group “nonequivalent” for the quasi-experimental design?
Because we did not use random assignment to place subjects in treatment groups, we cannot assume that on the average the groups are the same, or equivalent, to begin with. • Other types of quasi-experimental designs are also analogous to their experimental counterpasts, such as the Pretest-Postest Design (and additional groups can be added to mimic the Solomon 4 Group). However, two types of design often conducted more with quasi-experimental situations include the time series design (sometimes called a “natural experiment”) and the case study. In the time series design, you have several observations over time. While you may have some type of experimental intervention, often “nature” does the experimenting for you: • A hurricane hits and you assess how well emergency personnel put new training and procedures in place. • New legislation requires all automobile drivers and passengers to wear seat belts. • A state eliminates affirmative action considerations in collegiate admissions polic
