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Content: Observational studies are also useful as a starting point in research. For example the researchers may be investigating a new area of research in order to produce hypotheses for future investigations such as experiments. On the other hand observational studies are difficult to replicate. Observations do not provide information about what participants are thinking or feeling. There is little or no control of extraneous variables in observational studies therefore we can not make cause and effect statements. There is also the problem of observer bias with observational studies. This occurs if the observers ? see? what they expect to see. A number of ethical issues can arise with observational studies including problems with a lack of informed consent and invasion of privacy.