to provide a measurement of a tendency toward abnormal behavior, the measurements provided by the instrument would have to be consistent with those of other instruments of proven reliability in the measurement of tendencies toward abnormal behavior. For most surveys, where an external standard of measurement may not be available, the pre-test serves to establish the validity of the questionnaire.
Reliability, as opposed to validity, is concerned with the accuracy and precision of a measurement procedure or an analytical procedure. A measurement procedure is, thus, reliable to the extent that it supplies consistent outcomes. Once again consider the desire to measure the height of a number of individuals in feet and inches. The instrument calibrated in feet and inches would be considered to be reliable, if it yielded consistent results in the measurement time-and-time-again of the same group of individuals. In the case of the measurement of tendencies toward abnormal behavior in individu
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