* As well as controlling the independent variable the experimenter attempts to eliminate unwanted extraneous variables. * Control over extraneous variables is usually greater than in other research methods. * Experimental design involves manipulating the independent variable to observe the effect on the dependent variable. This makes it possible to determine a cause and effect relationship. * Because of strict conditions and control the experimenter can set up the experiment again and repeat or ‘check’ their results. Replication is very important as when similar results are obtained this gives greater confidence in the results. Disadvantages:
* Elimination of extraneous variables is not always possible. * Experimental situation may not relate to the real world. * It may be unethical or impossible to randomly assign people to groups. Eg. :
* Unethical to deliberately deprive children of sleep.
* Impossible (expensive) to observe ‘jetlag’ by sending people on world trips. * Unethical to experiment on forms of punishment on children by subjecting them to punishment.
* Advantages and Diadvantages of the Quantitative Observational Design. Advantages:
* Quantitative observational designs allow variables to be investigated that would be unethical, impossible or too costly under an experimental design. * Some kinds of behaviour can only be observed in a naturalistic setting. Disadvantages:
* Cannot infer such a strong cause and effect relationship because there is or greater chance of other variables affecting the results. This is due to the lack of random assignment to groups. * Cannot replicate the findings as the same situation will not occur naturally again. * Quantitative Observational does not allow generalisation of findings to the general population. * Observer bias may influence the results.