1. The researcher needs to control all possible variables, in order to test a hypothesis as accurately as possible.
  2. The way in which a researcher may affect the outcome of an experiment: the researcher’s expectations may (sometimes unconsciously) affect the response of the subjects.
  3. Getting informed consent from participants may affect the results; the participants’ experience should not be harmful, either during or after the experiment; one group should not be advantaged over another.
  4. Because of the high level of control, an experiment can be replicated easily; it is an objective method; it produces quantitative data.
  5. A high level of control means that what happens in the laboratory may not be true in the outside world; the small sample may not be representative; the participants may behave differently because they know they are in an experimental situation.
  6. Internal validity – if the results would be true for the participants outside the laboratory situation. External validity –if the results would be true for other individuals in the wider population.
  7. They both aim to test a hypothesis by manipulating one or more variables. Unlike the artificial laboratory environment, a field experiment takes place in natural surroundings.
  8. Advantages might be: it may be used to study the past; there are no potential ethical problems; it does not involve an artificial situation. Disadvantages might be: there is less control possible; there is more potential for experimenter effect.