There are seven basic project management tools used in project management and one of these seven tools is the scatter diagram. These tools are important for planning, monitoring and controlling different issues related to the quality within the organization. Scatter diagrams are correlation charts that utilize regression lines to predict how the change in the independent variables (X) will change the dependent variables (Y).
The direction of the correlation may be proportional (positive relationship), inverse (negative relationship) or may not exist at all (zero correlation). Establishing a correlation to understand how the dependent variable can strongly influence the dependent variable is used to make better decisions for the project.
If this particular project management quality tool can establish a relationship between two variables, a regression line can be calculated to estimate how the change of the independent variable will affect the value of the other variable.
Many people confuse scatter diagram with the fishbone diagram. The scatter diagram is entirely different from another basic quality tool called the fishbone diagram. The former lets project managers analyze relationships between two variables but the latter helps determine the effect of a specific root cause.
This term is defined in the 5th edition of the PMBOK.