Validity and Reliability Matrix Essay Example | Topics and Well Written Essays - 1250 words

Validity and Reliability Matrix - Essay Example Validity and Reliability Matrix This form of reliability is used to judge the consistency of results across items on the same test. Essentially, test items that measure the same construct are measured to determine the tests internal consistency. The multiple indicators of a property increase the measure's reliability. Rival hypotheses are ruled out because of the use of range of multiple indicators of the property being studied and measured. This test often helps researchers interpret data and predict the value of scores and the limits of the relationship among variables. A property is measured in several different ways, in which the most typical form for measurement is through questionnaire, and then measures obtained were combined into a single score, hence reliability across different parts of an instrument might be difficult to establish. The measures are specifics of a property which will eventually be collated to reflect a single information. Half of the test items (even numbered) are correlated to other half (odd numbered) to obtain reliability coefficient. This is done by randomly dividing all items that purport to measure the same construct into two sets. The entire instrument is administered to a sample of people and the total score for each randomly divided half is calculated. The split-half reliability estimate is simply the correlation between these two total scores. It only requires a single test administration. It is therefore resources-wise test. Cost and time will be used efficiently. It is limited to estimating differences on one dimension (usually the number of items, or raters). The resultant coefficient will vary as a function of how the test was split. It is also not appropriate on tests in which speed is a factor (that is, where students' scores are influenced by how many items they reached in the allotted time). Test/retest It is an index of score consistency over a brief time period, typically several weeks. It tells how much the individual's normative score is likely to change on near-term retesting. This index of score is obtained by administering the same test twice, with a certain amount of time between administrations, and then correlating the two score sets. Each subject should score different than the other subjects, but if the test is reliable then each subject should score the same in both test. The closer the results, the greater the test-retest reliability of the survey instrument. The test is easy to administer hence, it is the most popular indicator of survey reliability. The consistency of a measure from one time to another is measured and assessed. It assumes that there will be no change in the quality or construct being measured. "It is an excellent measure of score consistency because it allows the direct measurement of consistency from administration to administration" (Lawrence, R. et al, 2001) Administration of test for the second time may produce the "practice effect" - respondents "learn" to answer the same questions in the first test and this affects their responses in the next test. Score change could be caused by day-to-day fluctuation in performance, or the individual's