Ellen Drost
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Reliability
Data obtained from behavioural research studies are influenced by random errors of measurement. Measurement errors come either in the form of systematic error or random error. A good example is a bathroom scale (Rosenthal and Rosnow, 1991). Systematic error would be at play if you repeatedly weighed yourself on a bathroom scale which provided you with a consistent measure of your weight, but was always 10lb. heavier than it should be. Random error would be at work if the scale was accurate, but you misread it while weighing yourself. Consequently, on some occasions, you would read your weight as being slightly higher and on other occasions as slightly lower than it actually was. These random errors would, however, cancel out, on the average, over repeated measurements on a single person. On the other hand, systematic errors do not cancel out; these contribute to the