This column is not about that popular movie from the 1950s, but about to what those practicing statistical process control (SPC) are referring when they mention that name. They mean the most important techniques they use. The sevenSPC techniques are the following:

1. Check Sheet – to collect historical cleaning data
2. Pareto Chart – to analyze past cleaning defects by their frequency of occurrence
3. Histogram – a plot of overall cleaning performance by it's frequency of occurrence
4. Defect Concentration Diagram – an image of the parts showing the locations where cleaning is poor
5. Cause-and-Effect Diagram – what you think it is
6. Scatter Diagram – any X vs. Y relationship between cleaning performance and potential cause
7. CUSUM Control Chart – to identify the need for action in a timelyand positive manner

Collectively, the focus of all seven is to identify and enable actions that enhance cleaning (or any) process stability, compliance, and performance. In this column, we'll cover the first three. Next month, we'll cover the last four.

CHECK SHEETS
It may seem arrogant or ignorant to tell professionals doing critical cleaning work that it is important for them to write down what happened so they will be able to identify the causes of it. But many don't do it!
A check sheet is an accounting of the problems noted, the number of times they occur, and when they occur. A check sheet is an operating log — expressedin tabular format. Who uses a check sheet?

• Operating personnel design and use check sheets to identify the type of problems (defects) that must be eliminated. If operations were consistently and uniformly acceptable, there would be little need for a check sheet.
• Supervisors and operators would normally complete a log of events for every shift worked. A check sheet could be prepared by anyone, supervisor or operator, from that information.

Why use a check sheet? To be able to use a Pareto Chart or a histogram.

THE PARETO CHART
A Pareto¹ chart is the sibling to the check sheet. A Pareto chart is used tographically summarize and display the relative importance of the differences between groups of data — often those provided within a check sheet.
Figure 1 is an example of a Pareto Chart. It can be used to answer significantquestions including:

• What are the largest issues involved with the cleaning machine (or any other part of any system)?
• Where should efforts be focused to achieve the greatest improvements?
• What 20% of sources are causing 80% of the problems (the 80/20 Rule)?