Friday, February 5, 2010

What is the difference between a true experiment and experimental designs?

I am completely confused on this question and I believe they are both the same thing, but I am not sure.What is the difference between a true experiment and experimental designs?
Hi. Within Psychology a true experiment is the name given to an experiment that seeks to isolate cause and effect of observed relationships between independent variables and dependent variables.





On the other hand, experimental designs can be categorised as independent samples, repeated measures and matched pairs (amongst others). If we are going to set up an experiment we will need to use a sample of people at some point. In an independent samples design the people tested in the experiment are all different. That is to say that the people (participants) who we choose to test complete all aspects of the experiment, but only once.





In a repeated measures design the sample of people that are used in the experiment carry out all aspects of the experiment. However, by manipulating the independent variable the output by the participant may change, so the participant will carry out all aspects of the experiment more than once.





For a matched-pairs definition, think of having two sample groups who are taking part in an experiment on attitudes. One a 'treated' group and one a control group. A matched-pairs design compares one member of the treated group with one member of the control group. Say, for instance, that an attitude test scored the participants and placed them in order highest to lowest. A matched pairs design would allocate each participant one to the treated group, the next to the control group, the next treated, the next control and so on. This would then allow that a repeated measures style experiment could be carried out on the sample groups but without some of the problems that are associated with the repeated measures design such as order effects (effects gained from the order in which people carry out aspects of the experiment).





There are more examples of experimental designs and lot's of advantages and disadvantages that are inherent within these. It is far to vast an area to be able to give a complete summary here but what i've put above is a start. To properly understand these terms then have a look at some research methods books such as Coolican (2004) Research Methods and Statistics in Psychology.





I hope this helps.

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