Which statement best describes validity in an investigation?

• A. It concerns whether the procedure can answer the question and control variables, not just follow a recipe.
• B. It requires the result to be identical in all repeats.
• C. It means the measurement has zero uncertainty.
• D. It is solely about the speed of data collection.

Answer: (A)

Validity is about whether the investigation truly tests what it intends to test. A valid study shows that the method can answer the question and that variables are controlled so that the observed effect comes from the factor being studied, not from other factors. In practice, this means designing a fair test where only one independent variable changes at a time and all other variables are kept the same, with measurements that properly reflect the effect.

For example, if you’re investigating how light affects plant growth, you’d keep water, soil, pot size, and temperature constant and only vary the light exposure. Any difference in growth can then be attributed to light, not to other variables. The other statements describe reliability (getting the same results on repeats), measurement uncertainty, or speed of data collection, which are not about validity.