What measurement scale allows for equally spaced intervals but does not have a true zero?

The measurement scale that allows for equally spaced intervals but does not have a true zero is the interval scale. This scale is characterized by the fact that the differences between values are meaningful and consistent, enabling a variety of arithmetic operations, such as addition and subtraction. However, the absence of a true zero point means that you cannot make multiplicative comparisons, such as stating that one value is "twice" as much as another.

For instance, temperature measured in degrees Celsius is a prime example of an interval scale. The difference between 10 degrees and 20 degrees is the same as the difference between 20 degrees and 30 degrees, showcasing equal intervals. However, zero degrees Celsius does not imply a complete absence of temperature; it is simply a point on the temperature scale, which illustrates the lack of a true zero.

In contrast, nominal scales categorize data without any quantitative value, ordinal scales rank data but do not assume equal intervals, and ratio scales have both equal intervals and a true zero, allowing for full descriptive statistics and the comparison of magnitudes. Understanding these distinctions is key to selecting the appropriate statistical methods for analyzing different types of data.