The average outgoing quality level represents the relationship between the quality of the incoming material and the quality of the outgoing material, assuming that rejected lots will be 100% inspected and all defective items will be replaced or reworked.
When the incoming quality is very good or very bad, the outgoing quality is usually good because of the sorting and reworking of the bad parts so they don't get through the process. When the incoming quality is mediocre, the outgoing quality gets worse and the % defective reaches a maximum known as the average outgoing quality limit (AOQL).
You must specify the lot size in order to calculate the AOQ and AOQL.
In this example, when the average incoming quality level is 1.5% defective, the average outgoing quality is 1.42% defective. When the average incoming quality level is 10.0% defective, the average outgoing quality is 0.956% defective. The incoming quality is worse than the outgoing quality because rejected lots will be 100% inspected and will have all nonconforming units replaced or reworked.
The worst average outgoing defect level (AOQL) of 2.603% defective occurs when the incoming quality level is 4.3% defective.
Acceptance Sampling by Attributes
Measurement type: Go/no go
Lot quality in percent defective
Lot size: 5000
Use binomial distribution to calculate probability of acceptance
Acceptable Quality Level (AQL) 1.5
Producer’s Risk (α) 0.05
Rejectable Quality Level (RQL or LTPD) 10
Consumer’s Risk (β) 0.1
Sample Size 52
Acceptance Number 2
Accept lot if defective items in 52 sampled ≤ 2; Otherwise reject.
Percent Probability Probability
Defective Accepting Rejecting AOQ ATI
1.5 0.957 0.043 1.420 266.2
10.0 0.097 0.903 0.956 4521.9
Average Outgoing Quality Limit(s) (AOQL)