According to Cohen and Swerdlik (2018), Reliability means to be consistent. In psychometric terms, the meaning of reliability is based on when something is said to be consistent. The book defines “a reliability coefficient is an index of reliability, a proportion that indicates the ratio between the true score variance on a test and the total variance” (Cohen & Swerdlik, 2018, p. 141). Moreover, in testing and assessment there exist three sources of error variance such as test construction, test administration, and test scoring and interpretation. The text state that a measurement error is everything that is associated with the process of the variable being measured instead of the variable being measured (Cohen & Swerdlik, 2018).
Internal consistency reliability coefficient = .92
According to Cohen and Swerdlik (2018), states that internal consistency reliability is when a one can obtain an estimation of a test being reliable without creating a different form of the test nor administering the same test twice to the same individual (Cohen & Swerdlik, 2018). Furthermore, a test that has an Internal consistency reliability coefficient = .92 means that the item on the test must relate to one another and it also means that there exists a strong relationship between the content of the test. As I mentioned at the beginning of the post reliability means to be consistent. The higher the coefficient, the more reliable the test is. A .92 means that the test has excellent reliability and it is acceptable.
Alternate forms reliability coefficient = .82
According to Cohen and Swerdlik (2018), states that alternate forms are different types of test that are built to be parallel. Hence, the reliability of the alternate forms refers to “an estimate of the extent to which these different forms of the same test have been affected by item sampling error, or other error” (Cohen & Swerdlik, 2018, p. 149). An example we can use is when a person is given two different versions of the same test at a different time.
Test-retest reliability coefficient = .50
According to Cohen and Swerdlick (2018), A test-retest reliability is when a test is administered twice at two different points of time. Moreover, one we have to evaluate the reliability of a test-retest that purport to measure is fairly stable over time (Cohen & Swerdlik, 2018).
The higher the coefficient, the more reliable the test is. .92 means that the test has excellent reliability and it is acceptable the higher, the greater. An Alternate forms reliability coefficient = .82 is still high reliability, and it is also acceptable. A test-retest is a correlation of the same test over two administrator which relates to stability that involves scores. The book states that the more extended time has, the higher the chances that the reliability coefficient will be lower. Therefore, the passage of time may be an error of variance (Cohen & Swerdlik, 2018). Thus, depending on what the individual has been through some traumatic event it may also create an error variance which will impact their score variance and which will change, and the reliability will be lower than if that individual did not have any traumatic event. Therefore, if it is below .50 is not considered to be a reliable test nor acceptable. The book also states that “If we are to come to proper conclusions about the reliability of the measuring instrument, evaluation of a test-retest reliability estimate must extend to a consideration of possible intervening factors between test administrations” (Cohen & Swerdlik, 2018, p. 146).
Cohen, R. J., Swerdlik, M. (2018). Psychological Testing and Assessment. [Capella]. Retrieved from https://capella.vitalsource.com/#/books/1260303195/