The Katz Index of Activities of Daily Living uses which type of measurement scale to identify the level of assistance required in self-care activities?

• A. Ordinal scale
• B. Nominal scale
• C. Interval scale
• D. Ratio scale

Answer: (B)

The important idea here is how the Katz Index captures levels of independence in basic self-care. Each activity is judged as either independent or needing help, and these judgments are summed to give an overall score that ranks a person along a spectrum from more independent to more dependent.

This ranking creates ordered categories—it's clear that one level of independence is higher or lower than another. However, the intervals between those levels aren’t guaranteed to be equal, and there isn’t a true zero point with meaningful equal units across the entire scale. Hence, the Katz Index uses an ordinal scale. It’s not a nominal scale (which would just label categories without order), and it’s not interval or ratio because it doesn’t assume equal distances between levels or a true, meaningful zero for arithmetic operations.