Classes are non-overlapping intervals of values (preferably of equal length), open on the left and closed on the right, that cover an entire range of [[Science/Scientific Method/Measurement|observations]]. Splitting it into classes of equal size, the **class width** is obtained by evenly dividing the [[Range|range]] ($\mathrm{\frac{range}{number\ of\ classes}}$), rounded up. The midpoint of a class is the average of its lower and upper bounds. [[Frequency]] also applies to classes.