ANSI ASQ Z1.4-2008 PDF

ANSIASQZSampling Procedures and Tables for Inspection by Attributes- ANSI/ASQ Z Sampling Procedures and Tables for Inspection by. This e-standard is a very minor revision of ANSI/ASQ Z (R), also referred to as ANSI/ASQ Z ANSI/ASQ Z Sampling Procedures and Tables for Inspection By. Attributes The FDA recognizes ANSI/ASQ Z as a General consensus standard.

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Skip to main content. Log In Sign Up. Published on IVT Network http: Sampling The views and opinions expressed in this paper are those of the individual author and should not z1.4-2008 attributed to any company with which the author is now or has been employed or affiliated.

ANSI/ASQ Z – Sampling Procedures and Tables for Inspection by Attributes

Sampling Procedures and Tables for Inspection by Attributes. It provides simple instructions on how to correctly select the sampling plan based on the population size and the acceptable risk. In addition, this paper provides a general overview of statistics behind the development of sampling plans. Sampling Procedures and Tables for Inspection by Attributes is an acceptance sampling system that provides tightened, normal, and reduced plans to be applied for attributes inspection for percent nonconforming or nonconformities per units.

The use of sampling tables provides a quicker way of selecting the sampling plan instead of developing a sampling plan using complex statistics. The standard provides instructions on how it is supposed to be applied; however, it is often misinterpreted. The common mistakes include, but not are limited to, the selection of incorrect sampling size, selection of incorrect acceptance criteria, or attribute plan used for variable data, etc.

Therefore, it is very important to properly interpret the standard and apply the inspection rules as they are prescribed. Incorrect application can result in regulatory observations. The Importance of Sampling Sampling is a regulatory requirement in the pharmaceutical industry. The current good manufacturing practice cGMP requires sampling plans to be defined as well as samples to be representative of the population and based on appropriate statistical criteria.

In acceptance testing by attributes, a sample is randomly taken and inspected against established specifications allowable number of defects. If the number of defects exceeds the allowable number of defects, then the entire lot is rejected. Sampling Procedures and Tables for Inspection by Attributes is one of the most frequently used plans by many pharmaceutical companies as well as other industries.


The standard provides various inspection plans without getting into complex statistics. The standard is intended for inspection of final product, components and raw materials, materials in process, and data and records. Acceptance sampling procedures became popular during World War II.

Dodge and others and became frequently used as standards. MIL-STD was a United States defense standard that provided procedures and tables for sampling by attributes pass or fail characteristic. Different AQLs may be designated for different types of defects critical, major, and minor. The standard divides inspection levels into two main categories: According to the standard, inspection Level II should be used unless otherwise specified.

The sampling acceptance criteria discrimination increases from special levels to general levels with Level III having the greatest discrimination. Special levels shall be used when relatively small sample sizes are required and large sampling risks can be tolerated. Inspection Rules Provisions for each sampling plan include normal, tightened, or reduced inspection. Normal inspection should always be conducted at the start of inspection.

When normal inspection is applied, tightened inspection can be implemented when two out of five or fewer consecutive lots failed normal inspection. When tightened inspection is applied, normal inspection can be implemented when five consecutive lots pass the tightened inspection. The reduced inspection can be used conditionally when the normal inspection passes for more than two consecutive lots. Inspection can be discontinued when 10 consecutive lots remain on tightened inspection.

The switching rule diagram is provided below. Sampling Plan Types Three types of sampling plans are provided: Figure 2 outlines the differences of each plan. Types of Sampling Plans. Single Sampling Plan Double Sampling Plan Multiple Sampling Plan This plan is based on accepting or These plans combine single sample Similar to double sampling, there rejecting the lot on one sample only. With double sampling plans, be many sampling sequences to there are three different conclusions: Although complicated, ini resample the lot.

If the lot is they may utilize smaller sample s resampled, the results are combined to accept the lot. However, if ther with the first sample. At the end of the second sample the lot is then either accepted or rejected.

Inspection Procedure The general xsq Figure 3 in designing the sampling plan is the following. Note, the sampling plan consists of a sample size and acceptance criteria at particular AQL. The correct use of these tables is discussed further.

The packaging defects can be classified into three major categories: Defect categories are divided based on criticality to product quality attributes. Each defect category is assigned a different AQL level. Table III provides a list of typical tablet packaging defect classifications. Minor A defect that does not affect product safety, Grease on the bottle, double code on the 4.


For each defect category, defects are also classified into different types. For instance, if inspecting a bottle for tablet count, closure, seal, label and carton defects, these defects are not added together since they are results of different packaging processes. Instead, these defects are added based on the product attribute tablet count, closure, etc.

Z1.4:2008 inspection levels

For instance, if the expected packaging lot size is 36, bottles, it would be as to test all 36, bottles, so a representative sampling size should be selected. Letter N corresponds to sample size of If AQL level desired is specified as 0.

Statistics Behind Sampling Plans Sampling by attributes is based on binomial distribution. The performance of sampling plan is given by the operating characteristic OC curve. The OC curve shows the probability, Pa, that a submitted lot will be accepted for any given fraction defective p.

To construct an OC curve, one needs to know the sample size n and the number of defects c one is willing to accept. Therefore, to compute probabilities for c below and above 2, to anso 0. Since the sample with up to c defects is accepted, the cumulative binomial distribution is used to compute the probability of acceptance, P.

Calculating Binomial Distributing Using Excel. Figure 5 shows the OC constructed by plotting Pa vs. With more samples we test, the probability of accepting a lot with defects decreases.

Thus if we claim that we accept zero defects and test a very small sample, in this case five samples, there is a high probability that we are accepting defects in the lot without being able to detect them. Summary In summary, correct statistical sampling is required by the pharmaceutical industry regulations. Understanding of ANSI sampling by attributes and correct application will help to avoid sampling mistakes and adq observations.

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