Final answer:
The measurement principle that defines the likelihood of obtaining the same results from repeated applications of an assessment to the same subject is known as reliability. Consistency is the key aspect of reliability, with the ambition that research instruments demonstrate stable results over time.
Step-by-step explanation:
Reliability refers to the consistency of a measure, meaning that a reliable measure yields the same results under the same conditions. In the field of psychological research and other areas where data collection is vital, it is important for instruments or tools used to collect data to do so in a consistent, reproducible manner. There are various types of reliability, such as inter-rater reliability, internal consistency, and test-retest reliability.
Test-retest reliability specifically relates to the concept described in the question, which is the stability of a test's scores upon repeated applications. A reliable scale, for example, should show that if the same amount of cereal is poured onto it repeatedly, it will show the same weight each time. However, this does not necessarily indicate accuracy or validity, which is about whether the scale measures what it is supposed to measure correctly. Researchers often aim to employ tools that are both highly reliable and valid to ensure quality in data collection.