When might a quasi-experimental design be chosen over an experimental design? What considerations must a researcher make when deciding which approach to take? What are the threats to validity and reliability is this design trying to control for?
A quasi experiment might be the only choice in cases when it is impossible to randomly assign people to one of the groups (control or experimental).
For example, if we want to examine the effects of intelligence on adults whose mothers smoked when they were pregnant. There is no way of taking a group of 100 people and saying "ok, you go into the group of smoking mothers, and you go into the non-smoking mothers". This has already been selected by default. Our control and ...
This solution of 331 words explains and compares quasi-experimental and experimental design approach. It discusses the threats to validity and reliability in each study design.