Is action research intended as a substitute for experimental or quasi-experimental research?
Emphatically not. Different research paradigms serve different purposes. It may with benefit be used in some situations where quasi-experimental designs are presently used. But there are other situations where experimentation or quasi-experimentation may be far better suited. For instance, you may wish to find out about a few variables, and the causal relationships between them. If so, experimental or quasi-experimental research will serve you much better than action research. Alternatively, you may wish to explore some organisation or group or culture in depth, and with low impact. For this, you may do better to use ethnographic or other qualitative methods. Action research methods are most likely to be appropriate when you do not know where to start, and do not have a lot of time to invest in the study. It is useful for exploratory research, where you do not yet have a very precise research question. But it is most valuable when you have to be responsive to the changing demands of a
