Question

How do you think using a EWMA chart versus a Shewhart control chart would/would not work in maintenance line of work?

Answer 1

Shewhart chart:-

Advantages in maintenance line of work-

• ease to implement
• ability to detect large process shifts

Disadvantages in maintenance line of work-

• Relatively insensitive to small process shifts. Example- application- more accurate when fuel consumption for engine needs to be checked on daily / weekly basis, not hourly basis

EWMA (or Exponentially Weighted Moving Average) Charts:-

Advantages in maintenance line of work-

• provide quicker detection, example- hence good for checking deviations in temperatures at different hot spots on a diesel engine generator

Disadvantages in maintenance line of work-

• Requires the estimates of in-control process parameters, obtained from an initial Phase, which can be conditional. Hence, it further will show varying performance
• If data is not time-ordered, then trends or shifts in the process may not be detected. Example- if data related to exhaust gas temperatures out of a boiler is not timely collected, then final results could be just conditional