Lesson 5 — PDCA, Defect Causes & Root Cause
Chapter 13 treats data as the output of processes. Repeatedly fixing the output while leaving the producing process unchanged is weak long-term control.
PDCA for Data Quality
PLAN
Understand consumer requirements, critical data, actual condition, scope, business impact, likely causes, and improvement options.
DO
Implement selected process/system changes, controls, training, rule implementation, and necessary remediation.
CHECK
Measure actual data repeatedly against approved rules and thresholds. Confirm that the improvement worked and that the process remains controlled.
ACT
Respond when monitoring reveals deterioration or new conditions. Correct as needed and restart improvement when rules, requirements, processes, or data change.
Typical restart triggers include threshold breach, new data in scope, new requirements, and changed standards/rules.
Five common cause families
- Lack of oversight — weak priority, governance, leadership, incentives, ownership, or quality measures.
- Data Entry Processes — poor usability, training, field design, list placement, edit checks, overloaded fields.
- Data Processing Functions — downstream blindness, inconsistent execution, stale rules, changed structures/mappings.
- System Design — missing referential/uniqueness constraints, weak Master/Reference controls, timing/type/design defects.
- Fixing Previous Issues — rushed patches or corrective work that creates new defects.
The fifth family is a reminder that bad remediation can itself become a new source of bad data.
Root-cause techniques named in the chapter
- Pareto analysis;
- fishbone/Ishikawa diagram;
- track-and-trace;
- process analysis;
- Five Whys.
Three different responses
- Correction repairs existing bad records.
- Root-cause remediation changes the factor creating recurrence.
- Prevention establishes controls so defects do not enter or propagate.
Often all three are needed. Existing bad data may require correction even after the cause is removed.
Source: pp. 434–441, 455–459.