About Histograms

Histograms are used to show numerical information in graphic form. They usually follow a bar-graph format. When the results of a study or a survey are transferred into graphic form, it makes it easier for readers to analyze the data and understand the significance of the numbers. Similarly to other graphs, histograms have an x and y axis.

History

The term "histogram" is from the Greek language, and was coined by Karl Pearson, a famous statistician. Simply stated, it means a "common form of graphical representation." It is unclear when histograms were first created, but they have been useful tools for quite some time. "The Commercial and Political Atlas," written by William Playfair and published in 1786, contained the oldest known bar chart. In 1859, Florence Nightingale used histograms to show the difference in mortality between civilians and the military.

Function

The purpose of a histogram is to put numerical information into graphic form so it is easier to understand. Histograms show the frequency with which, and the time at which, certain things occur. For example, Florence Nightingale tried to show that military men died more frequently than civilians, which gave her the evidence she needed to improve army hygiene. When facts are visualized and labeled, it can help to make positive changes in the world.

Features

On the y-axis, histograms show the frequency with which something occurs. On the x-axis, the time is labeled. The x-axis is in even increments so the data doesn't look skewed. Data is then transferred into bar shapes for each increment on the x-axis. A stem-and-leaf-plot can be used to generate the data for a histogram. The leaf is the last digit of the number, and the remaining numbers are the stem. For example, the number 345 would have 5 as its leaf and 34 as its stem. You can create two columns--one for the stems and one for the leaves. You then lump the leaves with the similar stems, if there are any. When you turn a stem-and-leaf-plot on its side, it creates a histogram.

Identification

When you are analyzing a histogram, you need to read all of the labels to fully understand what the histogram is trying to show. First, read the title and find out what the main idea of the histogram is. Then look at the scale and the labels on the x and y axes. From there, you can determine the frequency for specific information, which can show a decrease, increase or pattern in the topic at hand.

Effects

Although histogram are simple graphs, they can provide valuable information. When numerical data is compressed and converted into a histogram, it enables readers to notice patterns and see changes. In order to improve institutions like health-care or education, you need to see the data and how it is being affected. However, not all histograms aim to change something. Some are simply for reference and to show basic statistical information about a certain topic.

Resources

• Stem-and-Leaf Plot Example