Reliability is one of the most important characteristics of a good test because it shows the consistency of your measurement. Assume that you are in the process of selecting an IQ test to administer to adults. In your own words, explain what it means to say that a test is reliable. Be sure to include in your discussion the components involved when estimating reliability such as the differences between observed scores and true scores, how standard errors of measurement and reliability coefficients provide indicators of reliability, how reliability is estimated, and the various factors that can affect the reliability of a test. Why is it important to estimate the precision of a score? How does reliability affect how much confidence one can place on an individual"s score?
(1) The reliability of a test
The reliability of a test measures its ability to measure a trait consistently (each time). For example, as an test examiner, you want a measure that is reliable in efforts to produce stable, scores that are not influenced by random error (i.e., by chance). In other words, if you are selecting an IQ test to administer, and you want to rely on the results. You want the be sure that you are measuring the same characteristic each time For example, if you are measuring intelligence as a characteristic, you will not want this characteristic to be unchanged from one situation to the next. For instance, if you measure the same person with the same characteristic at two different times, you would expect to obtain the same results.
(2) Observed Scores and True Scores
An observed score is an assessment of an individual's ability and performance and is made up of an individual's true score and error score. A person's true score is the expected number-correct score over a number of independent administrations of the test. True scores are used ...
This solution discusses the analysis and reliability of tests