R O X O
There are three types of experimental designs. They are:
* Pre-experimental designs
* True experimental designs and
* Quasi-experimental designs.
Pre-experimental designs lack random assignment to the program group and
the control group.This design illustrates some inherent weaknesses in terms of
establishing internal validity. The better designs are called true experimental designs
and quasi-experimental designs. True experimental designs are more complex
and use randomization and other techniques to control the threats to internal validity.
Quasi-experimental designs (Trochim, 2006) are special designs for use in the approximation of
true experimental control in nonexperimental settings. The closer your nonequivalent group
approximates a true experimental population the stronger the internal validity.