Chapter 18: Is/Is Not Analysis: The Underused Tool That Impresses Auditors

Here's a method that auditors notice—and respect—when they see it done right: Is/Is Not analysis. It's forensically precise. It narrows the problem definition before RCA even begins, which saves you from chasing false leads.

The method is simple: define what *is* happening and what *is not* happening, using very specific parameters. This comparison reveals the variables that matter.

A food-packaging plastics plant in Quebec experienced a recurring out-of-spec thickness defect on film destined for a major Canadian food brand. It was happening only on the second shift, only on the 2.5-millimeter film grade, and only on Wednesdays and Thursdays. Frustrating and weird.

Here's their Is/Is Not analysis:

The comparison revealed something striking: the defect was confined to a narrow operating window. Why only second shift? Because the 2.5mm film spec had the tightest tolerance, and Line B's extrusion head showed greater temperature drift as the shift progressed and ambient temperature dropped. The resin lot variation was immaterial—the common thread was the time-of-day thermal drift on equipment running a low-tolerance product.

The corrective action wasn't "train operators better." It was "pre-warm Extruder Line B during startup on second shift" and "adjust the extrusion temperature setpoint upward by 3°C specifically for 2.5mm film runs between 2:00 PM and end of shift." Forensic. Precise. Effective.

Important: During ISO 9001 internal audits or third-party registration audits, auditors look for evidence of disciplined problem-solving. Is/Is Not demonstrates that you didn't just guess at the problem; you narrowed it systematically. It's in your CAR file as proof of the thinking process. Auditors from major Canadian registrars (such as BV Canada and SCC-accredited registrars) explicitly note in audit reports that Is/Is Not evidence demonstrates systematic, not reactive, problem-solving.

When to use Is/Is Not: Always start here when a nonconformance is intermittent or variable. If it happened "sometimes" or "in certain conditions," Is/Is Not will reveal the pattern. It's also excellent when you have enough data to fill out the matrix (multiple occurrences, detailed capture of when and where). Pair it with fishbone or 5-Why afterward to explain the causes underlying the Is/Is Not pattern.