http://www.ck12.org Chapter 8. Organizing and Displaying Data for Comparison
The second type of line graph is known as a broken-line graph. In a broken-line graph, the slope represents the rate
of change, and they-intercept is actually the starting point. The graph below is a broken-line graph:
When the measurements began, the number of sales (they-intercept) was 645. The graph shows a significant increase
in the number of sales from weeks 5 through 10 and a significant reduction in the number of sales from weeks 16
through 20.
In this concept, you will be learning about comparing 2 line graphs that each contain data points. In statistics, when
line graphs are in the form of broken-line graphs, they are of more use. Linear functions (i.e.,y=mx+b) are more
for algebraic reasoning.Double line graphs, as with any double graphs, are often called parallel graphs, due to the
fact that they allow for the quick comparison of 2 sets of data. In this and the following Concepts, you will see them
referred to only as double graphs.
Example A
Thomas and Abby are training for the cross country meet at their school. Both students are in the 100 yard dash.
The coach asks them to race 500 yards and time each 100 yard interval. The following graph represents the times
for both Thomas and Abby for each of the five 100 yard intervals.