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The remainder of this discussion focuses on external validity and content validity.Įxternal validity is the extent to which the results of a study can be generalized from a sample to a population. There are numerous statistical tests and measures to assess the validity of quantitative instruments, which generally involves pilot testing. As a process, validation involves collecting and analyzing data to assess the accuracy of an instrument. It is rare, if nearly impossible, that an instrument be 100% valid, so validity is generally measured in degrees. Validity is the extent to which an instrument measures what it is supposed to measure and performs as it is designed to perform. It is best to use an existing instrument, one that has been developed and tested numerous times, such as can be found in the Mental Measurements Yearbook. Have any problems been reported by others who used it?.For now, we can identify five usability considerations: Validity and reliability concerns (discussed below) will help alleviate usability issues. Teachers are asked about their attitudes regarding school policy, but some questions are worded poorly which results in low completion rates (problem with scoring/interpretation).Students are asked to keep self-checklists of their after school activities, but the directions are complicated and the item descriptions confusing (problem with interpretation).Students are asked to rate a lesson immediately after class, but there are only a few minutes before the next class begins (problem with administration).Usability refers to the ease with which an instrument can be administered, interpreted by the participant, and scored/interpreted by the researcher. Examples are listed below: Researcher-completed Instruments

Researchers chose which type of instrument, or instruments, to use based on the research question. Instruments fall into two broad categories, researcher-completed and subject-completed, distinguished by those instruments that researchers administer versus those that are completed by participants. To help distinguish between instrument and instrumentation, consider that the instrument is the device and instrumentation is the course of action (the process of developing, testing, and using the device). Instrument is the general term that researchers use for a measurement device (survey, test, questionnaire, etc.).