Chapter 3 - Histograms: Looking at the Distribution of Data

Abstract

This chapter discusses about histograms and distribution of data. The first step toward understanding a list of numbers is to view its histogram to see its basic properties, such as typical values, special values, concentration, spread, the general pattern, and any separate groupings. A histogram is a picture that gives a visual impression of many of the basic properties of the data set as a whole. The histogram displays the frequencies as a bar chart rising above the number line indicating how often the various values occur in the data set. The horizontal axis represents the measurements of the data set (in dollars, number of people, miles per gallon, or whatever), and the vertical axis represents how often these values occur. An especially high bar indicates that many cases have data values at this position on the horizontal number line, while a shorter bar indicates a less common value. This chapter describes concepts of histograms, bar charts, skewed distribution, and data transformation along with bimodal distributions and data mining with histograms.