Which statement best distinguishes between interval and ratio levels of measurement?

• A. Interval variables can be ordered while ratio variables cannot, and interval variables permit multiplication and division but ratio variables only allow addition and subtraction, so their arithmetic rules are inverses of each other in that way.
• B. Interval and ratio are identical except that interval refers to categorical ranks and ratio refers to continuous percentages; the distinction is historical and usually ignored in applied statistics.
• C. Interval data allow meaningful differences but no true zero; ratio data have a meaningful zero and support ratios.
• D. Interval data have categories with no numerical operations allowed, whereas ratio data are always nominal labels with ordering but no meaningful arithmetic beyond list operations.

Answer: (C)