Reliability

Reliability

            When selecting an IQ test to administer, one must consider the reliability of the testing.  Reliability is defined as the coherence of the instrument in conjunction with the information collected using said instrument as the data is gathered over time.  It is the repeatability of the measurement which determines the degree to which the test is consistently effective (Russ-Eft & Preskill, 2009).  Additionally, when estimating reliability various components should be considered.  Such factors include the differences between observed scores and true scores, how standard errors of measurement and reliability coefficients provide indicators of reliability, how reliability is estimated, and the various factors that can affect the reliability of a test.  The following discussion expounds on these topics.

            First, as part of the IQ test selection process observed scores and true scores ought to be defined.  Observed scores consist of every measurement taken for each test, whereas the true score marks the constant measure.  Furthermore, each observed score contains the true score in addition to a degree of error (Thorndike & Thorndike-Christ, 2009).  A test example is a typing assessment.  Typically, an individual’s words per minute (wpm) are recorded.  If an individual is applying for various administrative assistant jobs, undoubtedly they are required to repeatedly complete a typing test for speed and accuracy.  Each of the test scores exhibits observed scores, as the constant wpm represents his or her true score.

            Second, in relation to reliability, standard errors of measurement and reliability coefficients are imperative.  The standard error of measurement refers to the typical discrepancy of measurement among scores.  More specifically, this expresses the common repeated measures in which the score deviates from the true or average score (Thorndike & Thorndike-Christ, 2009).  Hence, the range of observed scores is consistent which supports the reliability of the test.  Concerning reliability coefficients, a constant relationship between varying elements throughout testing demonstrates reliability.  Order is maintained from test to test regardless of the observed scores.  Both concepts, standard error of measurement and reliability coefficients, are interrelated in estimating reliability.  Given time limitations, researchers often utilize a couple of measurements to approximate the average scores and deviations as well as the order of the set.  Observance of the scatter sustains reliability.  In addition, it is important to estimate the precision of a score in effort to verify whether the level of variability is due to errors in measurement versus an inconsistency in true scores.  Also, this process “represents a more exacting definition of the test’s ability to reproduce the same score (Thorndike & Thorndike-Christ, 2009, p. 137).

            The final points of discussion are the factors affecting reliability and the correlation between reliability and the level of confidence one can place on an individual’s score.  In general, there are four factors affecting reliability; variability of the group, level of the group on the trait, length of the test, and operations used for estimating the reliability.  First, variability of the group refers to the consistency of order.  In cases in which order is maintained, the reliability coefficient is more precise.  However, if the order varies from test to test, reliability is adversely affected.  Second, the level of the group on the trait regards the experience or proficiency of participants in relation to the featured characteristic.  Hence, test accuracy may vary considering field goal percentages among a group of high school basketball shooting guards versus field goal percentages of a group of NBA shooting guards.  The third factor affecting reliability is the length of the test.  Generally, the longer the test the more accurate the scores are due to the fact that mannerisms or performance are repetitively displayed.  Last of these, operations used for estimating reliability are critical.  In short, various methods of testing provide varying levels of reliability (Thorndike & Thorndike-Christ, 2009).  Now, in regard to reliability and confidence, there is a direct correlation.  The more reliable the test, the more confidence one can place on an individual’s score.  Thus, an unreliable test results in less confidence concerning the accuracy of the outcome.       

References

Russ-Eft, D., & Preskill, H. (2009). Evaluation in organizations: A systematic approach

to enhancing learning, performance, and change (2nd ed.). New York:

Basic Books.

Thorndike, R. M. & Thorndike-Christ, T. M. (2009). Measurement and evaluation in psychology and

            education (8^th ed.).  Upper Saddle River, NJ: Prentice Hall.