Quality Improvement Zone

A Pareto chart is a bar chart that helps teams identify the factors contributing most to a problem. By displaying categories from highest to lowest frequency, it highlights the areas where improvement efforts may have the greatest impact.

A Pareto chart combines:

• Bars that show the frequency or size of each category.
• A cumulative percentage line that shows the combined contribution of categories as you move across the chart.

This makes it easier to identify the "vital few" categories that contribute most to an overall effect and may be the best place to focus further investigation and improvement efforts.

The Pareto Principle suggests that a relatively small number of factors often account for a large proportion of the overall effect. This is commonly referred to as the 80/20 rule, although the exact proportions will vary depending on the situation.

Pareto charts help teams focus their attention on the areas that may have the greatest impact. They can be used to prioritise improvement efforts, identify areas that require further investigation and communicate priorities using data.

Pareto charts can help you:

• identify which categories contribute most to a problem or outcome
• prioritise improvement efforts and make best use of available resources
• identify areas that may require further investigation
• communicate priorities clearly using data and visual displays
• support evidence-based decision-making
• explore reasons for patterns seen in counts, percentages or rates over time

Examples of where a Pareto chart may be useful include:

• types of safety incidents that occur
• causes of a specific problem
• reasons for cancellations
• sources of complaints
• distribution of waste generation across different parts of a service

Pareto charts require data that can be grouped into categories and counted. The chart can then help you identify which categories appear most significant and where you may wish to focus your attention.

1. Define the problem you want to understand

Start by identifying the issue, outcome or area you want to explore. Consider what information would help you better understand the problem and where improvement efforts should be focused.

2. Gather and organise the data

Use existing data sources, such as incident reports, complaints, audit results or other records, or collect data specifically for your analysis. Organise the data into categories relevant to the question you are exploring.

Pareto charts work best when they are based on a sufficient amount of data. As a guide, having more than 30 observations across the categories can help reduce the influence of random variation.

3. Create the Pareto chart

Count the number of observations within each category and arrange the categories from highest to lowest frequency. Plot these as bars and add a cumulative percentage line across the chart. In Excel, you can do this by selecting the data to highlight it. Then, go to the menu bar at the top of the screen, and select Insert. Select the histogram icon, and you will be presented with two options; select the one with the cumulative line.

4. Identify the "vital few"

Review the chart to identify the categories that account for the largest proportion of the overall effect. These categories may represent useful starting points for further investigation or improvement work.

5. Investigate before acting

A Pareto chart helps identify where to focus attention, but it does not explain why differences exist between categories. The largest category is not necessarily the cause of the problem. Additional investigation may be needed to understand the factors contributing to the pattern observed.

6. Use your findings to inform improvement

The insights gained from a Pareto chart can help inform further investigation and improvement work. Findings may be explored in more detail using tools such as process maps, cause and effect diagrams, driver diagrams and run or control charts.