A First Course in Statistics, 12th Edition

1.4 Types of Data

You have learned that statistics is the science of data and that data are obtained by measuring the values of one or more variables on the units in the sample (or population). All data (and hence the variables we measure) can be classified as one of two general types: quantitative data and qualitative data.

Quantitative data are data that are measured on a naturally occurring numerical scale.* The following are examples of quantitative data:

*Quantitative data can be subclassified as either interval data or ratio data. For ratio data, the origin (i.e., the value 0) is a meaningful number. But the origin has no meaning with interval data. Consequently, we can add and subtract interval data, but we can’t multiply and divide them. ...