Root Cause Analysis

Root cause analysis investigates how an unwanted outcome arose and which underlying conditions contributed. It aims to support changes that reduce recurrence. A symptom describes what was observed; a cause statement explains a mechanism and the conditions under which it operated. There may be several contributing causes rather than one deepest cause.

If pumps fail inspection after a software update, first establish whether the failures reflect defective pumps, changed acceptance limits, or an unreliable measuring instrument. Then trace software versions, calibration procedures, maintenance records, and affected production lots. The fact that one event happened after another is a reason to investigate, not sufficient evidence of causation.

An immediate correction, such as replacing a defective unit, addresses that instance. Containment limits current exposure while investigation continues. Corrective action addresses a supported cause or control weakness to reduce recurrence. Sending new instructions is an action record; it does not demonstrate that calibration is correct or that defects will not return.

Keep the proposed mechanism, supporting and contrary evidence, action owner, and outcome check together. A cause need not be under the investigating team’s control: another owner or a protective measure may be needed. Report what was observed over a stated population and period. No defects in one tested batch does not prove a zero future defect rate.

Examples are illustrative.

References:

• ASQ: Root Cause Analysis