A reader wrote to me and asked the following question about sampling plans by attributes: What is the "Confidence Level" when using the AQL Tables? How can we determine what the confidence levels are, and are there formulas we can use? That's a valid question. When playing with statistics, one often mentions a confidence interval. For example, "90% of the time, the value will be between 34.5 and 66.0". In theory, I guess one could do the same with the values in the AQL tables. There is a … [Read more...]
When To Do a Random AQL Inspection vs. Check 100% of the Goods
First, let me get one thing out of the way: not all batches need to be checked. If a manufacturer has great systems and processes, and if they have a history of complying with your quality standard, there is usually no reason to send quality inspectors to their facility. Similarly, if you can easily return the whole batch and it can be reworked quickly, you probably don't want to spend resources on checking whether they did as promised. Now, let's assume you do want confirmation of … [Read more...]