Problem:
When selecting an IQ test for adults, reliability refers to the degree to which the test produces consistent results over time, across items, or across forms rather than fluctuating due to random error. In classical test theory, an observed score is conceptualized as the sum of a true score and an error component. The true score represents the individual's actual standing on the construct being measured, and the error reflects unwanted influences such as fatigue, item sampling, or distractions during testing. The greater the proportion of true-score variance relative to error variance, the higher the test's reliability (Thorndike & Thorndike-Christ, 2009). Reliability is commonly expressed through reliability coefficients that estimate the proportion of observed score variance attributable to true differences among examinees. Coefficients approaching 1.00 indicate stronger reliability, whereas coefficients closer to zero indicate measurements dominated by error. Multiple approaches can be used to estimate these coefficients, including test-retest procedures that evaluate stability over time, internal consistency methods that examine the coherence of item responses, and alternate form comparisons that evaluate consistency across parallel forms (Thorndike & Thorndike-Christ, 2009). Need Assignment Help?