Intrroduction

nstrumentation refers to the tools or means by which investigators attempt to measure variables or items of interest in the data-collection process. It is related not only to instrument design, selection, construction, and assessment, but also the to conditions under which the designated instruments are administered—the instrument is the device used by investigators for collecting data.

In addition, during the process of data collection, investigators might fail to recognize that changes in the calibration of the measuring instrument(s) can lead to biased results. Therefore, instrumentation is also a specific term with respect to a threat to internal validity in research. This entry discusses instrumentation in relation to the data-collection process, internal validity, and research designs.

Thesis Statement

Impact of Instrumentation over Data Collection and Validity

Instrumentation Pertaining to the Whole Process of Data Collection

Instrumentation is the use of, or work completed by, planned instruments. In a research effort, it is the responsibility of an investigator to describe thoroughly the instrument used to measure the dependent variable(s), outcome(s), or the effects of interventions or treatments. In addition, because research largely relies on data collection through measurement, and instruments are assigned with operational numbers to measure purported constructs, instrumentation inevitably involves the procedure of establishing instrument validity and reliability as well as minimizing measurement errors.

Validity and Reliability

Validity refers to the extent to which an instrument measures what it purports to measure with investigated subjects. Based on the research necessities, investigators need to determine ways to assess instrument validity that best fits the needs and objectives for the research. In general, instrument validity consists of face validity, content validity, criterion-related validity, and construct-related validity. It is necessary to note that an instrument is simply valid for measuring a particular purpose and for a designated group. That is, an instrument can be valid for measuring a group of specific subjects but can become invalid for another.

Reliability refers to the degree to which an instrument consistently measures whatever the instrument was designed to measure. A reliable instrument can generate consistent results. More specifically, when an instrument is applied to target subjects more than once, an investigator can expect to obtain results that are quite similar or even identical each time.

Such measurement consistency enables investigators to gain confidence in the measuring ability or dependability of the particular instrument. Approaches to reliability consist of repeated measurements on an individual (i.e., test retest and equivalent forms), internal consistency measures (i.e., split-half, Kuder Richardson 20, KuderRichardson 21, and Cronbach's alpha), and interrater and intrarater reliability. Usually, reliability is shown in the numerical form, as a coefficient. The range of reliability coefficient is from 0 (errors existed in the entire measurement) to 1 (no error in the measurement was discovered); the higher the coefficient, the better the reliability.

Measurement Errors

Investigators need to attempt to minimize measurement errors whenever practical and possible for the purpose of accurately indicating the reported values collected by the instrument.

Measurement errors can occur for various reasons and might result from the conditions of testing (e.g., test procedure not ...