To calculate the comparative ratio known as Body Mass Index (BMI), an absolute measure of height and weight is needed. Such data is known as which of the following?
a. nominal data
b. interval data
c. ordinal data
d. Ratio data
The correct answer and explanation is:
The correct answer is d. Ratio data.
Explanation:
Body Mass Index (BMI) is a measure that requires height and weight as inputs. These inputs are considered ratio data, which is a type of quantitative data where both differences and ratios are meaningful. For example, it makes sense to say someone weighs twice as much as another person, and that they are, for instance, 50 cm taller than someone else. The ratios between these values have consistent meaning and the data has an absolute zero point, making it ratio data.
In more detail:
- Ratio data is characterized by having a true zero, meaning zero represents the complete absence of the attribute being measured. In the case of weight and height, zero weight means the absence of weight, and zero height means the absence of height.
- For BMI, both weight (measured in kilograms or pounds) and height (measured in meters or feet) are measured on a ratio scale, because you can have a meaningful zero value (i.e., a person with zero weight or zero height).
In contrast:
- Nominal data consists of categories with no inherent order or ranking. Examples include gender, ethnicity, or type of car. These categories do not allow for any meaningful mathematical operations.
- Ordinal data involves categories with a defined order, but the distances between the categories are not consistent or measurable. For example, a scale from “poor” to “excellent” represents ordinal data.
- Interval data also involves numerical measurements, but it does not have a true zero point. For example, temperature measured in Celsius or Fahrenheit is interval data because zero degrees does not mean the complete absence of temperature. It is an arbitrary point.
Therefore, height and weight are ratio data because they allow for meaningful calculations, comparisons, and have a true zero point.