years ago the stone exterior was deteriorating at the Jefferson Memorial in Washington DC a popular monument in the United States repairing the stone or painting over the worn areas was too expensive so park rangers turned to root cause analysis and started asking why why was the stone deteriorating high-powered sprayers were being used to wash the memorial every 2 weeks why were high-powered Washings needed every 2 weeks because of bird droppings asking why stopped because it seemed the cause was found workers put Nets around the building but they were unsightly and the birds found ways around them so it was back to the drawing board or the five wi's why are there so many birds they come to feed on spiders why are there so many spiders they feed on insects at night why are there so many insects they're attracted by lights that shine on the memorial at night with a new cause found question stopped and a plan was created to reduce the amount of time the memorial spent in the spotlight at night and it worked the insects were reduced by 90% And with the root cause removed the excessive cleaning was no longer needed an unexpected benefit was a cost savings realized by using less electricity this highlights how root cause analysis can involve trial and error and how the five wise isn't always limited to exactly five questions read more about root cause analysis and the Jefferson Memorial story at the link below what