Sampling and Quality Control
Why sample?
Random sampling
What does random sampling mean?
Binomial coefficients
How to do it?
Two views on sampling and Quality.
Sampling with and without replacement.
Simple vs. stratified random sampling
Sampling and SPC

Sampling with and without replacement.
If we randomly sample n distinct items from a Population of N items, this is simple random sampling without replacement. This is what is typically done in SPC.
If each time we randomly sample one item at a time return it, randomly sample another, etc., this is sampling with replacement. From a theoretical standpoint, this mimics sampling from an infinite (or hypothetically infinite) population.
A hypothetically infinite population could be all future production of a type of part, or it might be all future transactions of a certain type.