SPC vs 4.20
Element 4.20 (I think that is what you mean) is Statistical Techniques. Statistical Process Control (SPC) is just one technique. There are many other techniques that can be used to verify product or process.
We must be very careful here. Many registrars do not believe that 4.20 can be called ‘not applicable’ (I share this concept). I know some service and TE companies that end up tracking useless things just to satisfy the auditor. It would be far better for you to identify areas that should be tracked statistically. My suggestion is look for two things.
First, anything that causes you [or your customers] pain. The second thing is any time you ask things like; “Have we got any data on this?” or “How many times has this happened?”, you might be asking whether statistical tracking might be in order.
Specifically, the TE supplement also says to include R&M stuff. [And we all know your customers are free with sharing data you need to come up with OEE, MTBF and MTTR, etc.

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