SPC vs EPC

Question 1

Both SPC and EPC aim to reduce process variability. What is the main difference:

Answer 1

SPC focusses on identifying assignable causes and base on a statistical framwork of hypothesis testing.

EPC aims to keep processes on target (= minimizing variability) and can remove sources of variability SPC can’t. EPC is based on parameter estimation.

Question 2

What are three important steps of EPC

Answer 2

1 Predict the next observation on the process
2 Have some other variable that we can manipulate in order to affect the process output
3 know the effect of this manipulated variable, so we can react accordingly at time t+1 to keep the process on target.

Question 3

Why is EPC a good complement to SPC? (two reasons)

Answer 3

EPC make no attempt to identify assignable causes that may impact the process but react to process upsets.
EPC schemes don’t make any effort to reduce assignable causes.