One of the main strengths of Participant Observation (PO) is that it often produces highly valid data compared to most other research methods. There are several reasons for this. Firstly, PO involves the researcher actively participating in the daily lives of the respondents, often over extended periods—sometimes lasting months or even years. This is also one of the few methods that allows researchers to observe individuals in their natural environment, capturing what people actually do rather than what they claim to do. Spending such an extended period in close contact with participants enables the researcher to collect in-depth qualitative data and develop an empathetic understanding of the respondents' perspectives, seeing the world through their eyes and understanding how they interpret their actions.

Additionally, PO is respondent-led during its early stages, which allows the research process to unfold naturally without a rigid structure imposed from the outset, as is common in quantitative methods such as pre-written questionnaires. This flexibility can lead to unexpected findings. For instance, Venkatesh's study of crack gangs revealed that these groups were embedded in their wider community and even provided financial support to some community members—insights that might not have emerged with a more structured approach.

There is debate among sociologists about whether covert or overt PO yields more valid data. On the one hand, covert research might seem more likely to capture natural behaviour because respondents are unaware of the researcher's presence. However, some sociologists argue that participants may be more honest with a "professional stranger"—someone who is not perceived as a member of the group—than with someone they believe to be part of the group, as in covert research. Furthermore, covert researchers may face suspicion or exaggerated behavior from participants trying to impress the "newcomer," as may have occurred in Macintyre's study of football hooligans.

While PO has strong validity, most sociologists agree it has poor reliability. This is because it is difficult to replicate due to the unique relationships built between researchers and participants and the long time periods required to conduct such studies. Covert research, in particular, lacks transparency, as it is harder to use secondary methods or involve others in verifying findings, making the research heavily reliant on the researcher's integrity.

Representativeness is another limitation of PO. Because it often focuses on small, specific groups, the findings cannot easily be generalized to larger populations. However, interpretivists argue that this trade-off is justified by the rich insights and depth of understanding the method provides.

Practically, Participant Observation is extremely time-consuming. Gaining access to respondents can take months, and the research itself may last for years. Analyzing the large volumes of qualitative data collected also requires significant time and effort. Securing funding for such prolonged research is another practical challenge. Covert research, in particular, presents unique difficulties: gaining access to groups without revealing the researcher's identity is tricky, and data collection is more challenging because researchers cannot record observations openly. However, one key advantage of covert research is that it may be the only feasible way to access certain deviant or criminal groups.

Finally, Participant Observation raises significant ethical concerns. The close contact between the researcher and participants can create risks of harm to the respondents, and ensuring anonymity is often impossible. Covert research, in particular, involves deceit, and researchers might even become involved in illegal activities if they are studying deviant groups. However, some sociologists argue that the value of the insights gained about such groups or behaviours can outweigh the ethical concerns. Interpretivists also point out that PO is one of the few methods where respondents are treated as equals and are given the opportunity to fully express their perspectives.

In conclusion, the usefulness of Participant Observation depends on the researcher's priorities and methodological stance. Positivists often reject PO because it lacks objectivity, is unsystematic, and cannot produce the large samples needed to identify correlations and make generalizations. Interpretivists, on the other hand, value PO for its ability to provide valid, in-depth insights and an empathetic understanding of respondents' lives. Despite its strengths, practical and ethical challenges often limit the feasibility of this method, making its application dependent on the specific research context.