Benefits: Grant and Wall (2009) identify five key benefits of quasi-experimentation:

1. Strengthening causal inference when random assignment and controlled manipulation are not possible or ethical;

2. Building better theories of time and temporal progression;

3. Minimizing ethical dilemmas of harm, inequity, paternalism, and deception;

4. Facilitating collaboration with practitioners;

5. Using context to explain conflicting findings.

Limitations: Harris et al. (2004) identify potential methodological flaws of quasi experiments in the studies conducted in medical disciplines. The lack of random assignment is the major weakness of the quasi-experimental study design. Associations identified in quasi experiments meet some requirements of causality, because the intervention precedes the measurement of the outcome. Also, the outcome can be demonstrated to vary statistically with the intervention. Thus, the question arises: Are there alternative explanations for the apparent causal association? If these alternative explanations are credible, the evidence is less than convincing.

The methodological principles that most often result in alternative explanations in quasi-experimental studies include the following: 

1. Difficulty in controlling for important confounding variables;
2. Results that are explained by the statistical principle of regression to the mean;  
3. Maturation effects (Harris et al., 2004).

In an interrupted time-series, maturation effects, for example, occur if the intervention being evaluated is a technique requiring training and a set of skills (Muir Gray, 2009).