What defines an interval scale?

An interval scale is characterized by having meaningful distances between the values it represents, indicating the precise difference in quantity, but it does not possess a true zero point. This means that while you can measure the difference between values (for example, the difference between 10 degrees and 20 degrees is the same as between 30 degrees and 40 degrees), a zero value does not imply the absence of the quantity being measured. For instance, in temperature measured in Celsius, 0 degrees does not mean there is no temperature; it's simply a point on the temperature scale.

The presence of meaningful intervals is crucial, as it allows for the calculation of mean and other statistical analyses that rely on the distance of the data points from one another. Therefore, answer C accurately captures the essence of what an interval scale is, distinguishing it effectively from other types of measurement scales that either lack meaningful distances or do not include a true zero point.