Explain what reliability is. Based on the sample statistics, is this test reliable? What evidence from the statistics supports your answer?

Referring to consistency and stability, reliability is the ability of an instrument or test to produce consistent results. Other words, reliability is how consistent a test can be across time, different testers, and different sections of the test. Different types of reliability exist, such as test-retest, inter-rater, and internal consistency.

According to the statistics in the text, the test appears to be reliable. Test-retest reliability (r), which is based on sample statistics, was 0.85. It indicates a high degree of consistency in the results of both administrations. It means that people who have taken the test two times got similar results both times. This indicates that the test measures something consistent and stable.

Additionally, the internal consistency reliability coefficient (Cronbach’s alpha) for the test is 0.90, which is considered to be a high level of consistency. The items of the test measure the same concept or construct, and not unrelated ones. The test must be reliable, valid and measuring the intended outcome.

Standard error of measurement is 2.5 for this test. This indicates how much error can be expected from a single score. SEM estimates the possible amount of errors that may occur as a result of factors like test taker variability and measurement error. Lower SEMs indicate a greater level of accuracy and reliability as they suggest that scores are not influenced by other factors.

Together, these statistics show that the test may be reliable. It is also important to remember that reliability of a test is not fixed and may vary due to factors like the conditions under which the test is administered, the sample population, or the method used for scoring. To ensure consistency and accuracy, it’s important to continuously assess the test’s reliability over time.

The sample statistics in the text book suggest that the test appears to be reliable. This is supported by the fact that test scores have a high reliability coefficient for test-retests, a low internal consistency reliability coefficient and standardized error. It would take more research to prove the reliability in various populations.