2.1. Histograms and Frequency Distributions http://www.ck12.org
2.1 Histograms and Frequency Distributions
Learning Objectives
- Read and make frequency tables for a data set.
- Identify and translate data sets to and from a histogram, a relative frequency histogram, and a frequency
polygon. - Identify histogram distribution shapes as skewed or symmetric and understand the basic implications of these
shapes. - Identify and translate data sets to and from an ogive plot (cumulative distribution function).
Introduction
In chapter 1, we focused on describing data using summary statistics. While this is very useful in analyzing and
learning important characteristics of a data set, it is also very important and informative to represent data in some
visual format. This is in fact the form in which most people are used to encountering data while engaged in such
things as reading newspapers, magazines, food labels, or watching television. Charts and graphs of various types,
when created carefully, can provide instantaneous important information about a data set without calculating, or
even having knowledge of, various statistical measures. This chapter will concentrate on some of the more common
visual presentations of data.
Frequency Tables
A Real Context: Recycling Issues
The earth has seemed so large in scope for thousands of years that it is only recently that many have begun to take
seriously the idea that we live on a planet of limited and dwindling resources that is in a sense, and island in the
middle of space. This is something that residents of the Galapagos Islands are also beginning to understand on a
much more dramatic level. Because of its isolation and lack of resources to support large, modernized populations
of humans, the problems that we face on a global level are magnified in the Galapagos, as well as other island
cultures. Basic human resources such as water, food, fuel, and building materials, must all be brought in to the
islands. More problematically, the waste products must either be disposed of in the islands, or shipped somewhere
else at a prohibitive cost. As the human population grows exponentially, the Islands are confronted with the problem
of what to do with all the waste. In most communities in the United States, it is easy for many to put out the trash
on the street corner each week and perhaps never worry about where that trash is going. In the Galapagos, the desire
not protect the fragile ecosystem from the impacts of human waste is more urgent and is resulting in a new focus on