Page 25 - Sociology and You

Line and Bar Graphs
A graph, like a picture, may present information in a more concise way than words. Line graphs and bar graphs are drawings that compare numerical val- ues. They often are used to compare changes over time or differences between places, groups of items, or other related events. Both types of graphs can be used to display the same information, and the choice between the two is often at the discretion of the author. In general, however, line graphs are used to show trends over time related to one type of data (e.g. percentage of the population that believes in God, average age at first mar- riage, or number of households headed by a single woman). Bar graphs may be used to show trends over time or to compare different types of informa- tion, such as median income for men and women or age groups of a pop- ulation.
Learning the Skill
Follow these steps to learn how to understand and use line and bar graphs.
◆ Read the title of the graph. This should tell you what to expect or look
for.
◆ Note the information on the left side of the graph—the vertical axis.
The information being compared usually appears on this axis.
◆ Note the information along the bottom of the graph—the horizontal
axis. Time often appears along this axis.
◆ Determine what the line(s) or bar(s) symbolizes.
◆ Select a point on the line or bar, then note the date below this point
on the horizontal axis and the quantity measured on the vertical axis.
◆ Analyze the movement of the line (whether increasing or decreasing
over time), or compare bars to determine the point being made.
Practicing the Skill
Review the graphs, then answer the questions. Note that both graphs pre- sent the same information.
1. About what percentage of families with children under 18 were headed by single parents in 1985? In 1996?
2. How would you describe the general trend shown by these graphs?
3. Based on the data for the last four years shown, can you state what the
current trend is for families headed by single parents?
4. Which graph represents this data in a more meaningful way?
Sociology Handbook HB-11