Minitab uses an algorithm to solve the following equations for n, sample size, and c, acceptance number.
Term | Description |
---|---|
α | producer's risk |
β | consumer's risk |
p1 | acceptable quality level (AQL) |
p2 | rejectable quality level (RQL) or lot tolerance percent defective (LTPD) |
0 < p1< p2< 1
The probability of acceptance (Pa) describes the chance of accepting a particular lot based on a specific sampling plan and incoming proportion defective. It is based on the binomial distribution.
Term | Description |
---|---|
c | acceptance number |
n | sample size |
p | fraction defective |
The probability of rejecting (Pr) describes the chance of rejecting a particular lot based on a specific sampling plan and incoming proportion defective. It is simply 1 minus the probability of acceptance.
Pr = 1 – Pa
where:
Pa = probability of acceptance
The average outgoing quality represents the quality level of the product after inspection. The average outgoing quality varies as the incoming fraction defective varies.
Term | Description |
---|---|
Pa | probability of acceptance |
p | incoming fraction defective |
N | lot size |
n | sample size |
The average total inspection represents the average number of units that will be inspected for a particular incoming quality level and probability of acceptance.
Term | Description |
---|---|
Pa | probability of acceptance |
N | lot size |
n | sample size |