Definition:Class Interval/Integer Data

Definition

Let $D$ be a finite collection of $n$ data regarding some quantitative variable.

Let the data in $D$ be described by integers.

Let $d_{\min}$ be the value of the smallest datum in $D$.

Let $d_{\max}$ be the value of the largest datum in $D$.

Let $P = \set {x_0, x_1, x_2, \ldots, x_{n - 1}, x_n} \subseteq \Z$ be a subdivision of $\closedint a b$, where $a \le x_0 \le x_n \le b$.

The integer interval $\closedint a b$, where $a \le d_{\min} \le d_\max \le b$, is said to be divided into class intervals of integer intervals of the forms $\closedint {x_i} {x_{i + 1} }$ or $\closedint {x_i} {x_i}$ if and only if:

Every datum is assigned into exactly one class interval

Every class interval is disjoint from every other class interval

The union of all class intervals contains the entire integer interval $\closedint {x_0} {x_n}$

By convention, the first and last class intervals are not empty class intervals.

Sources

• 2011: Charles Henry Brase and Corrinne Pellillo Brase: Understandable Statistics (10th ed.): $\S 2.1$