A Pareto chart is a line and bar graph that provides a visual illustration of a problem. Pareto charts can be created using Microsoft Excel or Open Office. The Pareto chart ranks the problem based on occurrences from left to right. The Pareto chart is used extensively in quality control; it can help a team focus improvement efforts on the most critical problem. Here is an example of a Pareto chart that ranks different types of errors that occurred in a blood donor center. From the chart, the most frequent error is "no collector initials." While this information is helpful, it is probably not specific enough. To achieve more meaningful data one can create another Pareto chart, breaking the "no collector initials" further down by site (mobile blood drive, donor center location) or by procedure type (apheresis, whole blood collection, autologous donation, etc).