The Psychology of Quality and More
Cause-Effect Diagram: Examples
The managing director of a weighing machine company received a number of irate letters, complaining of slow service and a constantly engaged telephone. Rather surprised, he asked his support and marketing managers to look into it. With two other people, they first defined the key symptom as 'lack of responsiveness to customers' and then met to brainstorm possible causes, using a Cause-Effect Diagram, as illustrated.
They used the 'Four Ms' (Manpower, Methods, Machines and Materials) as primary cause areas, and then added secondary cause areas before adding actual causes, thus helping to ensure that all possible causes were considered. Causes common to several areas were flagged with capital letters, and key causes to verify and address were circled.
On further investigation, they found that service visits were not well organized; engineers just picked up a pile of calls and did them in order. They consequently set up regions by engineer and sorted calls; this significantly reduced traveling time and increased service turnaround time. They also improved the telephone system and recommended a review of suppliers' quality procedures.
Fig. 1. Example Cause-Effect Diagram
And the big