reliability and validity

• Reliability and validity are two terms that are constantly seen together in research and scientific texts.^[1]

Definition: Reliability refers to the consistency and stability of a measurement or test. A reliable test produces similar results when administered under consistent conditions.

• Example: If you weigh yourself on a scale and get the same reading every time you step on it, the scale is reliable. If the scale gives different readings each time, it is not reliable.^[2]

Definition: Validity is the degree to which a test or measurement accurately assesses what it intends to measure. A valid test measures the concept or skill it claims to measure.

• Example: Imagine you have a thermometer that is supposed to measure body temperature. If it consistently (always) gives accurate readings close to your actual body temperature, it is a valid thermometer. If it often shows incorrect temperatures, it lacks validity.^[2]

Reliability: If a stopwatch consistently records the same time for an event when used multiple times, it is reliable. On the other hand, if the stopwatch shows different times for the same event, it is not reliable.

Validity: If a driving test accurately assesses a person's ability to drive safely, it is a valid test. However, if the test measures unrelated skills or fails to capture important aspects of driving, it lacks validity.

Imagine you have a friend who is helping you test a new video game. Reliability is like having your friend play the game multiple times and getting consistent scores each time. If your friend gets different scores every time they play, it wouldn't be reliable because the results are not consistent.

Validity is like making sure your friend is actually testing the game and not, for example, just pressing random buttons. If your friend is playing the game properly and the scores reflect how good or bad the game is, then the test is valid.

So, in simple terms, reliability is about getting consistent results, and validity is about making sure the test measures what it's supposed to measure. ^[3]

In summary, reliability is about consistency, and validity is about accuracy in measuring what it's supposed to measure. Reliable measurements are consistent, while valid measurements accurately reflect the intended concept or skill.^[3]