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Test developers have the responsibility of reporting the reliability estimates that are relevant for a particular test. Before deciding to use a test, read the test manual and any independent reviews to determine if its reliability is acceptable. The acceptable level of reliability will differ depending on the type of test and the reliability estimate used.
The discussion in Table 2 should help you develop some familiarity with the different kinds of reliability estimates Compare and assess the three alternative in test manuals and reviews.
Types of Reliability Estimates Test-retest reliability indicates the repeatability of test scores with the passage of time.
This estimate also reflects the stability of the characteristic or construct being measured by the test. Some constructs are more stable than others. For example, an individual's reading ability is more stable over a particular period of time than that individual's anxiety level. Therefore, you would expect a higher test-retest reliability coefficient on a reading test than you would on a test that measures anxiety.
For constructs that are expected to vary over time, an acceptable test-retest reliability coefficient may be lower than is suggested in Table 1. Alternate or parallel form reliability indicates how consistent test scores are likely to be if a person takes two or more forms of a test.
A high parallel form reliability coefficient indicates that the different forms of the test are very similar which means that it makes virtually no difference which version of the test a person takes.
On the other hand, a low parallel form reliability coefficient suggests that the different forms are probably not comparable; they may be measuring different things and therefore cannot be used interchangeably. Inter-rater reliability indicates how consistent test scores are likely to be if the test is scored by two or more raters.
On some tests, raters evaluate responses to questions and determine the score. Differences in judgments among raters are likely to produce variations in test scores. A high inter-rater reliability coefficient indicates that the judgment process is stable and the resulting scores are reliable.
Inter-rater reliability coefficients are typically lower than other types of reliability estimates. However, it is possible to obtain higher levels of inter-rater reliabilities if raters are appropriately trained. Internal consistency reliability indicates the extent to which items on a test measure the same thing.
A high internal consistency reliability coefficient for a test indicates that the items on the test are very similar to each other in content homogeneous.
It is important to note that the length of a test can affect internal consistency reliability. For example, a very lengthy test can spuriously inflate the reliability coefficient.
Tests that measure multiple characteristics are usually divided into distinct components. Manuals for such tests typically report a separate internal consistency reliability coefficient for each component in addition to one for the whole test. Test manuals and reviews report several kinds of internal consistency reliability estimates.
Each type of estimate is appropriate under certain circumstances. The test manual should explain why a particular estimate is reported. Standard error of measurement Test manuals report a statistic called the standard error of measurement SEM. It gives the margin of error that you should expect in an individual test score because of imperfect reliability of the test.
The SEM represents the degree of confidence that a person's "true" score lies within a particular range of scores. For example, an SEM of "2" indicates that a test taker's "true" score probably lies within 2 points in either direction of the score he or she receives on the test. This means that if an individual receives a 91 on the test, there is a good chance that the person's "true" score lies somewhere between 89 and The SEM is a useful measure of the accuracy of individual test scores.
The smaller the SEM, the more accurate the measurements. When evaluating the reliability coefficients of a test, it is important to review the explanations provided in the manual for the following: Types of reliability used.
The manual should indicate why a certain type of reliability coefficient was reported. The manual should also discuss sources of random measurement error that are relevant for the test.
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Chapter 3: Understanding Test Quality-Concepts of Reliability and Validity Test reliability and validity are two technical properties of a test that indicate the quality and usefulness of the test. These are the two most important features of a test.
You should examine these features when evaluating the suitability of the test for your use. Simple ways to assess the writing skills of students with learning disabilities. A teacher's first responsibility is to provide opportunities for writing and encouragement for students who attempt to write.
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