In terms of validity, observational research findings are considered to be strong. Trochim states that validity is the best available approximation to the truth of a given proposition, inference, or conclusion. Observational research findings are considered strong in validity because the researcher is able to collect a depth of information about a particular behavior. However, there are negative aspects. There are problems with reliability and generalizability.
Reliability refers the extent that observations can be replicated.
Seeing behaviors occur over and over again may be a time consuming task. Generalizability, or external validity, is described by Trochim as the extent that the study's findings would also be true for other people, in other places, and at other times. In observational research, findings may only reflect a unique population and therefore cannot be generalized to others. There are also problems with researcher bias. Bias, however, can often be overcome with training or electronically recording observations.