Experimental methods
Experimental methods
Having recorded a signal, it is necessary to interpret its functional significance. The way in which this is done is to relate the signal to a psychological condition. As in other branches of science, an experimental condition is contrasted with a control condition. The interpretation is clearest when these differ in just one respect, though this can be difficult to achieve. Standard statistics are used to evaluate the significance of the difference. However, the analysis of imaging data can be onerous and many methods have been developed to avoid false-positive and false-negative results. These include robust correction for the number of statistical comparisons that are made, as the image is made up of thousands of voxels across many regions. Researchers also use targeted region-of-interest analysis; in this case the region must be specified beforehand. One must also study enough subjects: if small groups are used, the study may be underpowered.
Keywords: control conditions, subtraction technique, false positive, false negative, type I error, type II error, replication, number of subjects
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