The totals that double every Friday
Every Friday the weekly totals are twice as big as they should be. Each time, an analyst deletes the extra rows and the report looks right again.
Deleting the rows treats a symptom. The real reason is still there, so the totals double again next week. To stop it for good, you must find the root cause.
By the end of this lesson
Note
I can use a root cause method to find the real reason for a fault and say what to do next.
Key words
| Word | What it means |
|---|---|
| Symptom | What you can see going wrong |
| Root cause | The real reason a fault happens |
| Five whys | Asking "why?" again and again until you reach the root cause |
| FMEA | A table that lists how things could fail and scores each one |
| Event tree | A diagram that follows one event through safety steps that work or fail |
| Log | Write down what happened and what was done |
| Escalate | Pass a problem to somebody with more skill or authority |
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A root cause stops a fault coming back
The purpose of root cause analysis is to find the real reason for a fault, so the fault does not return.
Use it when a fault repeats, when it is serious, or when a fix only hides it. A quick fix is fine for a one-off. A root cause is needed for the Friday totals.
Method one: the five whys
Ask "why?" about the symptom. Then ask "why?" about the answer. Keep going, about five times, until you reach a cause you can fix.
It is fast and needs no tools. It works well for faults with one chain of causes.
Five whys: the Friday totals
| Question | Answer |
|---|---|
| Why are the totals twice as big? | Every sale appears two times |
| Why does every sale appear twice? | The sales file was loaded two times |
| Why was it loaded two times? | Two load jobs run on Friday |
| Why do two jobs run? | An old job was never switched off |
| Why was it never switched off? | Nobody keeps a list of jobs. This is the root cause. |
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.