Independent Measures Design
An independent measures design is a research method in which multiple experimental groups are used and participants are only in one group. Each participant is only in one condition of the independent variable during the experiment.
An example would be a drug trial for a new pharmaceutical. To test the effect on the disorder and discover any side effects an independent measures design could be used. The researchers use two different conditions: group A who receives the drug and group B who receives a placebo (a fake pill). The participants would be randomly assigned to one of the two groups- for it to be an independent measures design each participant would either be in group A or B, not both. Advantages of independent measures design include less time/money involved than a within subjects design and increased external validity because more participants are used. A disadvantage is that individual differences in participants can sometimes lead to differences in the groups' results. This can lead to false conclusions that the different conditions caused results when it was really just individual differences between the participants. Random sampling can help with this problem.