Show  Psychological Testing and Assessment: An Introduction To Tests and Measurement, 5/e Alternate forms Different versions of the same test or measure; contrast with parallel forms, 132 Coefficient alpha Also referred to as Cronbach's alpha and alpha, a statistic widely employed in test construction and used to assist in deriving an estimate of reliability; more technically, it is equal to the mean of all split-half reliabilities, 137-138 Coefficient of equivalence An estimate of parallel-forms reliability or alternate-forms reliability, 132. Coefficient of generalizability In generalizability theory, an index of the influence that particular facets have on a test score, 147 Coefficient of stability An estimate of test-retest reliability obtained dur-ing time intervals of six months or longer, 132. Confidence interval A range or band of test scores that is likely to contain the "true score," 149-150 Content sampling Also referred to as item sampling, the variety of the subject matter contained in the items; frequently referred to in the context of the variation between individual test items in a test or between test items in two or more tests, 129 Criterion-referenced testing and assessment Also referred to as domain-referenced testing and assessment and content-referenced testing and assessment, a method of evaluation and a way of deriving meaning from test scores by evaluating an individual's score with reference to a set standard (or criterion); contrast with norm-referenced testing and assessment, 30, 109, 112 Error variance In the true score model, the component of variance attributable to random sources irrelevant to the trait or ability the test purports to measure in an observed score or distribution of scores. Common sources of error variance include those related to test construction (including item or content sampling), test administration, and test scoring and interpretation, 18, 129 Generalizability theory Also referred to as domain sampling theory, a system of assumptions about measurement that includes the notion that a test score, and even a response to an individual item, is composed of a relatively stable component that actually is what the test or individual item is designed to measure, and relatively unstable components that collectively can be accounted for as error, 145, 147-148 Inflation of range Also referred to as inflation of variance, a reference to a phenomenon associated with reliability estimates wherein the variance of either variable in a correlational analysis is inflated by the sampling procedure used and the resulting correlation coefficient tends to be higher as a consequence; contrast with restriction of range, 141 Internal consistency Also referred to as inter-item consistency, an estimate of how consistently the items of a test measure a single construct obtained from a single administration of a single form of the test and the measurement of the degree of correlation among all of the test items, 135, 205-206 Inter-scorer reliability Also referred to as inter-rater reliability, observer reliability, judge reliability, and scorer reliability, an estimate of the degree of agreement or consistency between two or more scorers (or judges or raters or observers), 138-139. Item response theory (IRT) Also referred to as latent-trait theory or the latent-trait model, a system of assumptions about measurement, including the assumption that a trait being measured by a test is uni-dimensional, and the extent to which each test item measures the trait, 148, 210n Item sampling Also referred to as content sampling, the variety of the subject matter contained in the items; frequently referred to in the context of the variation between individual test items in a test or between test items in two or more tests, 129 Kappa statistic A measure of inter-scorer reliability originally designed for use when scorers make ratings using nominal scales of measurement, 139 Kuder-Richardson formulas A series of equations developed by G. F. Kuder and M. W. Richardson designed to estimate the inter-item consistency of tests, 136-137 Odd-even reliability An estimate of split-half reliability of a test, obtained by assigning odd-numbered items to one-half of the test and even-numbered items to the other half, 134. Parallel forms Two or more versions or forms of the same test when for each form, the means and variances of observed test scores are equal; contrast with alternate forms, 132 Power test A test, usually of achievement or ability, with (1) either no time limit or such a long time limit that all testtakers can attempt all items, and (2) some items so diffi-cult that no testtaker can obtain a perfect score; contrast with speed test, 142 Reliability The extent to which measurements are consistent or re-peatable; also, the extent to which measurements differ from occasion to occasion as a function of measurement error, 29, 32, 128-153 Reliability coefficient General term for an index of reliability or the ratio of true score variance on a test to the total variance, 128, 139-148. Restriction of range Also referred to as restriction of variance, a phenomenon associated with reliability estimates wherein the variance of either variable in a correlational analysis is restricted by the sampling procedure used, and the resulting correlation coefficient tends to be lower as a consequence; contrast with inflation of range, 141 Rulon formula Now outdated, an equation once used to estimate internal consistency reliability, 137 Spearman-Brown formula An equation used to estimate internal consistency reliability from a correlation of two halves of a test that has been lengthened or shortened; inappropriate for use with heterogeneous tests or speed tests, 134-135 Speed test A test, usually of achievement or ability, with a time limit; speed tests usually contain items of uniform difficulty level, 142 Split-half reliability An estimate of the internal consistency of a test obtained by correlating two pairs of scores obtained from equivalent halves of a single test administered once, 133-135. Standard error of measurement In true score theory, a statistic designed to estimate the extent to which an observed score deviates from a true score; also called the standard error of a score, 19, 148 Standard error of the difference A statistic designed to aid in determining how large a difference between two scores should be before it is considered statistically signifi-cant, 150-152 Test heterogeneity Also simply heterogeneity, the extent to which individual test items do not measure a single construct but instead measure different factors; contrast with test homogeneity, 135-136, 141 Test homogeneity Also simply homogeneity, the extent to which individual test items measure a single construct; contrast with test heterogeneity, 135, 136, 174 Test-retest reliability An estimate of reliability obtained by correlating pairs of scores from the same people on two different administrations of the same test, 131-132. True variance In the true score model, the component of variance attributable to true differences in the ability or trait being measured, inherent in an observed score or distribution of scores, 129 Variance A measure of variability equal to the arithmetic mean of the squares of the differences between the scores in a distibution and their mean, 87, 88, 129 What is testTest-retest reliability is a measure of reliability obtained by administering the same test twice over a period of time to a group of individuals. The scores from Time 1 and Time 2 can then be correlated in order to evaluate the test for stability over time.
Which term refers to scores on an assessment being fairly similar over time?Reliability refers to the consistency of a measure. 1 A test is considered reliable if we get the same result repeatedly. For example, if a test is designed to measure a trait (such as introversion), then each time the test is administered to a subject, the results should be approximately the same.
What is reliability a proportion of?Reliability is defined as the proportion of true variance over the obtained variance. reliability = true variance / obtained variance. = true variance / (true variance + error variance) A reliability coefficient of .
Which statistical tool is used only for calculating the internal consistency of a test in which items are dichotomous?Cronbach's alpha is a measure used to assess the reliability, or internal consistency, of a set of scale or test items.
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