Which of the following best illustrates the concept of valid measurement?

The concept of valid measurement focuses on the accuracy and relevance of what is being measured in relation to the intended purpose. A thermometer measuring temperature precisely exemplifies valid measurement because it accurately reflects the temperature being measured, providing true and relevant data. The precision of the thermometer ensures that the readings are reliable and can be trusted for making decisions based on temperature, which is crucial in many scientific and everyday contexts.

In contrast, other options illustrate various issues with measurement validity. A ruler that changes its length does not provide a stable reference for measurement, making it unreliable. A survey that collects data on irrelevant factors fails to gather pertinent information that addresses the research question, thus compromising the validity of the findings. Similarly, a clock that is consistently fast does not convey the correct time, leading to misleading conclusions about time-related activities. In summary, valid measurement requires both accuracy and relevance, as demonstrated clearly by the thermometer example.