One bar represents the number of boys who use the Internet and the other bar represents the girls.
#DATAGRAPH SERIAL NUMBER SERIES#
However, if a group vertical bar graph has too many series of data, the graph becomes cluttered and it can be confusing to read.įigure 2, a double vertical bar graph, compares two series of data: the numbers of boys and girls using the Internet at Redwood Secondary School from 1995 to 2002. This allows you to make direct comparisons on the same graph by age group, sex, race, or anything else you wish to compare. This type of vertical bar graph gives two or more pieces of information for each item on the x-axis instead of just one as in Figure 1. The double (or group) vertical bar graph is another effective means of comparing sets of data about the same places or items. For example, in 2001 there were nine more police officers than in 1998. The graph also makes it easy to compare or contrast the number of police officers for any combination of years. In Figure 1 you can see that the number of police officers decreased from 1993 to 1996, but started increasing again in 1996.
Figure 1 below shows the number of police officers in Crimeville from 1993 to 2001.
At a glance you can see from the graph that the scales for both the x- and y-axis increase as they get farther away from the origin. The space for labels on the x-axis is small, but ideal for years, minutes, hours or months. From the information given in the section on graph types, you will know that vertical bar graphs are particularly useful for time series data. Example 1 – Vertical bar graphsīar graphs should be used when you are showing segments of information. However, in general, data comparisons are best represented vertically. There are three types of graphs used to display time series data:Īll three of these types of graphs work well when you need to compare values. Select an arbitrary but consistent width for each bar as well. The height or length of the bar will represent the number of units or observations in that category (frequency) or simply the value of the variable. When developing bar graphs, draw a vertical or horizontal bar for each category or value. The numbers on the x-axis of a bar graph or the y-axis of a column graph are called the scale. The bars depict frequencies of different values of a variable or simply the different values themselves. They consist of an axis and a series or labeled horizontal or vertical bars. The important point to note about bar graphs is their bar length or height-the greater their length or height, the greater their value.īar graphs are one of the many techniques used to present data in a visual form so that the reader may readily recognize patterns or trends.īar graphs usually present categorical and numeric variables grouped in class intervals. A bar graph may be either horizontal or vertical.
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