Module 7 · Process Improvement with BPMN and Lean
Root cause analysis
Get from a symptom to the causes you can actually fix with a fishbone diagram, five whys and Pareto analysis, and avoid the classic trap of confusing a high rate with a big total.
About 20 minutes
The problem
Incomplete documents cause Harbourline's most expensive wait. Before the pilot, clearances with incomplete documents spent 11.1 days at port on average, against 7.4 for complete ones, and paid almost twice as much demurrage per container. So why are documents incomplete?
The clearing team's answer is "customers are careless". That's a symptom with a label on it, not a cause, and you can't fix "careless". Root cause analysis keeps asking until it reaches something specific that can be changed: a missing form, an unclear instruction, a permit nobody mentions until it's too late.
The concept
The fishbone (Ishikawa) diagram
Write the problem at the "head" and brainstorm causes along six "bones":
| Category | Questions for incomplete documents |
|---|---|
| People | Do customers know what's needed? Does Harbourline's team? |
| Process | When does Harbourline ask for documents? Is there a checklist? |
| Policy | Which goods need extra permits (NAFDAC, SONCAP)? Do the rules change? |
| Materials (inputs) | Which documents are most often missing or wrong? |
| Systems | How are documents sent and stored? Can versions get mixed up? |
| Measurement | Does anyone track incompleteness by customer or document? |
The fishbone generates candidate causes. Data and five whys test them.
Five whys, applied:
- Why are documents incomplete? The permit is missing.
- Why? The customer didn't know it was needed.
- Why? Harbourline only lists the required documents after the vessel arrives.
- Why? The documentation team checks files on arrival, not before.
- Why? That's how the process was set up when shipments were simpler.
Root cause: documents are checked too late for problems to be fixed before arrival. That's something Harbourline controls.
Pareto analysis: rate versus count
Sort the causes (or customer groups) by how many problems they cause, and look at the cumulative share. Usually a few account for most. But compare two measures:
- the rate: which group is most likely to have the problem?
- the count: which group causes the most problems in total?
A small group with a very high rate needs a targeted fix. A large group with a moderate rate may cause more problems overall.
Example
Incomplete documents before the pilot, by importer type:
| Importer type | Clearances | Incomplete | Rate |
|---|---|---|---|
| Pharmaceutical | 33 | 23 | 70% |
| Manufacturer | 95 | 30 | 32% |
| Retailer | 89 | 26 | 29% |
| Electronics | 63 | 17 | 27% |
| Construction | 47 | 15 | 32% |
Pharmaceutical importers are by far the most likely to have incomplete documents (they need NAFDAC permits that others don't), so they need a specific fix: a permit check weeks before shipping. But manufacturers and retailers together cause more incomplete files (56) than pharmaceuticals (23). A fix aimed only at pharmaceutical importers would miss most of the problem. A general "check before arrival" fix reaches everyone.
Walkthrough
- Compare days at port and demurrage per container for complete and incomplete files, before the pilot.
- Draw a fishbone for "documents incomplete on arrival", with at least two causes per bone.
- Run five whys on the most likely cause.
- Build the table in the example and a Pareto chart of incomplete files by importer type.
- Write the root causes you'll act on, each with its evidence (the task below).
Practice
Practice
Before the pilot, what was the average demurrage per container for clearances with incomplete documents on arrival? (Total demurrage ÷ total containers, for those cases. A rounded figure is fine.)
Practice
Before the pilot, what share of all incomplete files came from Pharmaceutical importers? One decimal place.
Task
8 minWrite five whys for a different problem: Customers wait an average of two days for Harbourline to confirm their duty payment. Number each why (1. to 5.), give an answer for each, and finish with a line starting Root cause: that names something Harbourline can change.
Your work is checked for
- Five numbered whys
- A Root cause line
- The root cause isn't just blaming people (careless, lazy, slow staff)
- Enough detail: at least 60 words
Check your understanding
Answer every question to check.