Scatter Plot

http://www.itl.nist.gov/div898/handbook/eda/section3/eda33q3.htm

Scatter plots simply show the relationship between two variables. Using a line of standard deviation one can see the trend and determine what type of relationship there is between the two variables. There can be a positive, negative, strong, and weak relationship between the variables depending on the data set. The scatter plot above shows a strong negative relationship.