Ordinal - Observations in one category are ordered relative to those in another. Numerical - Observations in one category are functionally related to those in another. This includes the familiar interval and ratio levels, as well as less famiar levels such as absolute and log-interval. These various levels differ in terms of the function relating observations between categories. Continuous - all observations in a category are represented by an interval of numbers.
Multivariate data are usually column conditional.
Matrix conditional - Only observations within matrices are comparable. Missing Data . There is only one observation category, so it is not possible to define between category relationships, so no measurement level can be defined. Therefore, missing data are the weakest level of measurement. However, they can have either measurement process.