Answer:
When groups are not equivalent, researchers can look at changes from pretest to posttest scores.
Explanation:
A nonequivalent control group
This is simply regarded as a control group that is set on certain previous (preexisting) descriptions or characteristics that is almost the same or similar to those observed in a treatment group and participants are not randomly assigned. it is said that in a quasi experiment, a dependent variable measured in a treatment group is compared to that in the nonequivalent control group.
A nonequivalent control group pretest-posttest design
In this type of design, it is said that the dependent variable is scored or measured in one group of participants before the pretest is made and also after the posttest, a treatment and that same dependent variable is also measured at pretest and posttest in another nonequivalent control group that does not receive the treatment. Here, the groups are not usually equivalent.
Advantages and disadvantages of the nonequivalent control group pretest-posttest design
Advantages
1. it is often used to rate or compare scores before and after a treatment in a group that receives the treatment and in a group that does not.
Disadvantages
1. it is prone to the threat of selection differences.
