Acceptance Sampling by Variables -
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Acceptance Sampling by Variables -
Create / CompareStat > Quality Tools > Acceptance Sampling by Variables > Create / Compare
Allows you to create a variables acceptance sampling plan or compare various sampling plans that you specify.
Create a sampling plan: Choose to determine a sample size and the criteria for accepting or rejecting an entire lot.
Compare user defined sampling plans: Choose to see how effective your current sampling plan is and to compare various competing plans.
Units for quality levels: Choose the units based on your measurement type. Choose either Percent defective (0-100), Proportion defective (0-1), or Defectives per million to represent the number of defectives in your sample.
Acceptable
quality level (AQL): Enter
a number to represent the largest number of defectives in a process that
will still be considered acceptable. Typically, a sampling plan is designed
to give a high probability of acceptance at the AQL.
You must specify the AQL when you create a sampling plan, but it is not
required for comparing sampling plans. The AQL must be consistent with
measurement units. For example, with percent defectives 0<AQL<100;
with proportion defective 0<AQL<1; and with defectives per million
0<AQL<1,000,000.
Rejectable
quality level (RQL or LTPD): Enter
a number to represent the number of defectives in an individual lot that
you are willing to tolerate. Typically, a sampling plan is designed to
give a low probability of acceptance at the RQL.
You must specify the RQL when you create a sampling plan, but it is not
required for comparing sampling plans. The RQL must be entered consistently
with measurement units and must be larger than the AQL. For example, with
percent defectives AQL<RQL<100; with proportion defective AQL<RQL<1;
and with defectives per million AQL<RQL<1,000,000.
Lower spec: Enter the lower specification limit. You must enter at least one specification limit.
Upper spec: Enter the upper specification limit. You must enter at least one specification limit. The upper spec must be greater than the lower spec.
Historical standard deviation (Optional): Enter a known positive value for the standard deviation of the measurements. Use this when you have collected enough data over time to state with confidence what your process standard deviation is.
Lot size: Enter a number to represent the lot size or batch size of the entire shipment that you will accept or reject based on sampling results. You don't need to specify a lot size if you specify the AQL, RQL, and alpha and beta risks; however, Minitab requires the lot size to calculate the AOQ curve and the ATI curve.
Producer's risk (Alpha): Enter a value between 0 and 1 to represent a. 1- a represents the desired probability of accepting a lot at the AQL, which is necessary for creating the sampling plan.
Consumer's risk (Beta): Enter a value between 0 and 1- a to represent b. b represents the desired probability of accepting a lot at the RQL, which is necessary for creating the sampling plan.
Sample sizes: Enter positive integers to specify the sample sizes you wish to compare.
Critical distances (k values): Enter positive values to specify the critical distances you wish to compare.
Use these guidelines to enter sample sizes and critical distances: