Explain reliability and validity with an example.

• A. A bathroom scale that gives 10 kg every time is reliable but not valid; valid scale would measure true weight.
• B. A scale that gives random readings is reliable and valid.
• C. Reliability and validity are the same concept.
• D. A measurement can be both reliable and invalid consistently.

Answer: (A)

Reliability is about consistency. If you measure the same thing under the same conditions, you should get the same result each time. Validity is about accuracy: the measurement must reflect the true value or the thing you intend to measure.

An example helps: a bathroom scale that always shows 10 kg. It’s reliable because the reading is consistent every time. But it’s not valid for measuring most people’s weight, since their true weight isn’t 10 kg. So the scale is reliable but not valid. A valid scale would read the true weight, and when properly calibrated, it would also be consistent.

This shows why reliability and validity are related but different. A measurement can be reliable (consistent) without being valid (accurate). The other statements either mix up the ideas or ignore the difference between consistency and truthfulness.