Typically the measurement of reliability is reflected in what is called a reliability coefficient. This is unlike a standard correlation coefficient where, usually, the coefficient needs to be squared in order to obtain a variance (Cohen & Swerdlik, 2005). Coefficients in the range 0.80-0.90 are considered to be very good for course and licensure assessments. Cronbach’s alpha can be written as a function of the number of test items and the average inter-correlation among the items. It is Reliability coefficients range from 0.00 to 1.00. It is denoted by the letter "r," and is expressed as a number ranging between 0 and 1.00, with r = 0 indicating no reliability, and r = 1.00 indicating perfect reliability. Technically speaking, Cronbach’s alpha is not a statistical test – it is a coefficient of reliability (or consistency). Again, an Alpha of … Test Reliability—Basic Concepts Samuel A. Livingston Educational Testing Service, Princeton, New Jersey. The correlation between one set of observations with the second, then, provides a reliability coefficient. January 2018 Corresponding author: S. A. Livingston, E-mail: slivingston@ets.org No learning effect was found when comparing the results of the second measurement with the first measurement (P>.05). Reliability study designs and corresponding reliability coefficients To estimate test-score reliability, at a minimum one needs at least two observations (scores) on the same set of persons (Tables 2a and 2b). High reliability coefficients are required for standardized tests because they are administered only once and the score on that one test is used to draw conclusions about each student’s level on the trait of interest. Reliability coefficients range from 1.00 (which is highest) to 0.00 (which is lowest). C. Reliability Standards. (Internal 4 Difficulty Item Difficulty represents the percentage of students who answered a test item correctly. This means that low item a reliability coefficient of .70 or higher. In reality, all tests have some error, so reliability is never 1.00. For good classroom tests, the reliability coefficients should be .70 or higher. ¨ A reliability coefficient can range from a value of 0.0 (all the variance is measurement error) to a value of 1.00 (no measurement error). Cronbach's Coefficient Alpha has become the most popular way of reporting estimates of the reliability of psychological measures. 2.3. Post hoc power analysis confirmed previous power analysis, that is, despite the small sample size, an excellent power was found for the observed interobserver reliability coefficients (power range, 0.93-1.00). The reliability of a test is indicated by the reliability coefficient. 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