Final answer:
A test that yields the same results over repeated applications has achieved reliability, which is the measure of a test's consistency. Reliability is necessary but not sufficient for a test's usefulness; it must also be valid, accurately measuring what it is intended to measure.
Step-by-step explanation:
When a test yields the same results over repeated applications, it has achieved reliability. Reliability is the consistency of a measure, which means that if the test is repeatedly administered under the same circumstances, it would produce the same results each time. This is a crucial quality measure in testing psychological constructs, educational assessments, and various types of research. While reliability is necessary for a test to be useful, it is not sufficient by itself; a reliable test might still not measure what it is supposed to measure, which is where the concept of validity comes into play. Validity refers to the accuracy of the test in measuring exactly what it is intended to measure. For researchers and educators, striving for both reliability and validity in their instruments is essential for producing meaningful and actionable results.