Using Quality Improvement Tools
Histograms
What: A graphical summary of the frequency distribution of a data set
Why: To identify patterns in process data that might be difficult to determine when looking at numbers
When: Your project involves analysis of continuous data (e.g. dosage size, temperature, time)
How:
- Sort and tally individual data points to determine the highest and lowest values
- Choose a cell width; narrower is typically better but you might find a need for anywhere fro m6-12 categories of equal width
- Determine category boundaries:
- Choose a starting point at or just below the lowest value
- Put values that fall on the boundary into the next highest cell
- Tally the number of data points in each cell
- Draw your bar chart [or use a template such as this one from our friends down south at the New South Wales Clinical Excellence Comission) using the vertical axis for category frequency and the horizontal axis for the variable values
This is a summary of the steps presented in the IHI guidelines on creating histograms.
Template: histogram Builder with Adjustable Bin Sizes
Template: From the American Society for Quality