Design offers the first and best opportunity for reducing variation. To illustrate the strategies and tools required, consider the task of designing a new pump. Suppose we are faced with the task of designing a pump capable of delivering solution at a constant rate of 10 ml/min. Customer usage requires that the flow rate remains …
INTRODUCTION An understanding of statistical principles and how to apply them is critical to ensuring compliance with FDA requirements, such as those in the current and July working draft of the good manufacturing practices (GMP) regulation. Indeed numerous Form 483’s issued by FDA following GMP inspections have cited sampling plans for final, in-process, and receiving …
Dr. Wayne A. Taylor For the OC curve, AQL, and LTPD of a sampling plan to be valid, one must obtain representative samples of the lot. Failure to select representative samples can seriously compromise the sampling plan’s protection. Consider the analogy of dealing cards to obtain a fair hand. If the deck is thoroughly shuffled, …
Dr. Wayne A. Taylor The use of SPC is preferable to relying on acceptance sampling. It is better to make defect-free product than to sort out the defects later. However, with attribute data, care must be taken in implementing SPC to avoid only an illusion of change. Suppose a packing operation inspects for missing parts …
Dr. Wayne A. Taylor Mil-Std-105E indexes sampling plans by AQL, Levels of Inspection, and lot size. It is a common misconception that 105E includes lot size because “larger lots require more samples to obtain the same level of protection.” In actuality, 105E takes more samples from larger lots in order to get better protection. Figure 1 …
Dr. Wayne A. Taylor Numerous 483’s issued by the FDA have cited sampling plans as not being “statistically valid”. So what is required of a sampling plan to be statistically valid? Selecting statistically valid sampling plans is a two-part process. First, one must determine an appropriate objective for the inspection. Second, one must select a …
Dr. Wayne A. Taylor It is common practice to classify defects accordingly to their severity and then to assign each category an acceptable quality level (AQL). How justified is this practice and what guidelines can be given in assigning AQLs? The answer to this depends on how AQL is interpreted. Most generally the AQL is …
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