### 1.2 Characteristics of the Data

(i.) Measurement Level: Whether the variables are measured on
a metric or non-metric scale

(ii.) Number of Variables

#### Data

*Data* is a set of organized information; it is a quantification or
measurement of the real world by a set of variables. Statistical data is a set
of observations on which values of variables are given. *Variables* are
things that one measures, controls or manipulates in a research problem.
Variables differ in respect of their role in research (whether independent or
dependent variables) and 'how well' they can be measured. The amount of
information provided by a variable depends upon the type of measurement scale
used for their measurement.

There are two types of data sets:

- Individuals - variables data sets
- Proximities data sets

*Individuals - variables* data set is a matrix (*n* × *p*) in
which the rows represent the individuals and columns represent the set of
variables. At each intersection of a row*, i,* and column*, j, *(*i.e*.
cell* i, j*) is a piece of information given by the variable*, j*,
for the individual, *i*.

*Proximities data set* is a matrix (*p* × *p*) or (*n* ×
*n*), in which the cell values (directly measured or calculated)
correspond to the distance between pairs of variables or pairs of individuals.
Thus, there are two types of proximities data sets: V*ariable - Variable
Proximities* and *Individual - Individual Proximities*.