Using Quality Improvement Tools

Scatter Diagram

What: A visual representation of the correlation between two variables

Why: An easy way to assess the relationship between two related numeric variables

When: If, when there is a good correlation between two variables, you're interested in using one variable to predict changes in the other

How:

  1. Collect the data points for your two variables
  2. Put the suspected causal variable on the X axis and dependent variable on the other
  3. Plot the X and Y pairs on the diagram [or use a template such as one of those below]
  4. Interpret:
    1. If both values increase as you move towards the right of the chart, the correlation is positive
    2. If one value decreases while the other increases the correlation is bnegative
    3. If the points are more circular or scattered, there is little or no correlation

This is a summary of the steps presented in the IHI guidelines for creating a scatter diagram.

Create a scatter chart in Excel

Template: From the American Society for Quality

Template: From the New South Wales Clinical Excellence Commission