Each datum belongs to a @dfn{case} (also called an @dfn{observation}).
Each case represents an individual or ``experimental unit''.
For example, in the results of a survey, the names of the respondents,
Each datum belongs to a @dfn{case} (also called an @dfn{observation}).
Each case represents an individual or ``experimental unit''.
For example, in the results of a survey, the names of the respondents,