7.1. Line Graphs and Scatter Plots http://www.ck12.org
The month of August had the highest sales for both years. Between the months and August and September there is a
great decrease in the ice cream sales. However, the month of December shows an unexpected increase in sales. This
could be due to the holiday season.
Scatter Plots
Often, when real-world data is plotted, the result is a linear pattern. The general direction of the data can be seen, but
the data points do not all fall on a line. This type of graph is a scatter plot. Ascatter plotis often used to investigate
the relationship (if one exists) between two sets of data. The data is plotted on a graph such that one quantity is
plotted on thex−axis and one quantity is plotted on they−axis. If the relationship does exist between the two sets
of data, it will be visible when the data is plotted.
Example 1:The following graph represents the relationship between the price per pound of lobster and the number
of lobsters sold. Although the points cannot be joined to form a straight line, the graph does suggest a linear pattern.
What is the relationship between the cost per pound and the number of lobsters sold?
Solution:
From the graph, it is obvious that a relationship does exist between the cost per pound and the number of lobsters
sold. When the cost per pound was low, the number of lobsters sold was high.
Example 2:The following scatter plot represents the sale of lottery tickets and the temperature.
Is there a relationship between the number of lottery tickets sold and the temperature?
Solution: