Section 1.2 Characterizing a Set of Measurements: Graphical Methods
An individual population (or any set of measurements) can be characterized by a relative frequency distribution, which can be represented by a relative frequency histogram. A graph is constructed by subdividing the axis of measurement into intervals of equal width. A rectangle is constructed over each interval, such that the height of the rectangle is proportional to the fraction of the total number of measurements falling in each cell… Although they are arbitrary, a few guidelines can be very helpful in selecting the intervals. Points of subdivision of the axis of measurement should be chosen so that it is impossible for a measurement to fall on a point of division… Using many intervals with a small amount of data results in little summarization and presents a picture very similar to that data in their original form. The larger the amount of data, the greater the number of included intervals can be while still presenting a satisfactory picture of the data. We suggest spanning the range of the data with from 5 to 20 intervals and using the larger number of intervals for larger quantities of data.
