One characteristic of a line plot that makes finding statistical landmarks easier to identify is the scale. A scale is a system of ordered marks at fixed intervals. For example, on an inch ruler, the inches are on a scale of one, meaning the inches increase by ones, from one to 12. On line plots, the scale is also set at intervals of one. A unique aspect of line plots is the scale is located on the "X" or horizontal axis, while on most graphs the scale is located on the "Y" or vertical axis.
Another unique characteristic of line plots is that they use variables or symbols to represent data instead of numbers. For example, a common variable used on line plots is the variable "X" and it serves to represent an object rather than a number. In some cases the variable stands to represent one object, but in other cases the variable can be stated to represent a number of the same objects. For example, the value of "X" can be made to equal one student or one "X" can be made to represent five students, depending on the number of pieces of data in a data set.
Because line plots use symbols to represent data, they must also include a key that explains what each symbol represents. Unless stated directly in the line plot, two pieces of information that need to be included in a key are what the symbols represent and the value of each symbol. For example, when using "X" to represent students, this should be stated in the key, and if the "X" represents five students rather than one, this must also be stated in the key as well.
As with all graphs, the title gives the reader clues as to what information is conveyed in the graph. Titles can be especially important in line plots because, again, you are using symbols to represent data, so the title can give clues as to what the symbols mean. This is especially helpful if this information is not shared in a key. The title can also help the reader understand the scale more accurately as well. For example, if the title is "How Many Books Did Fifth-Graders Read Last Summer," the reader can infer that the numbers in the scale are the number of books read by an individual student.