After you create a variables acceptance sampling plan to determine the sample size and acceptance criteria for each incoming lot, you can analyze the measurement data from a sample to determine whether to accept or reject an entire lot of a product. Collect a sample, according to the plan sample size, and record the measurements of a single measured characteristic, such as thickness, concentration, or surface roughness. Minitab uses your data from particular lots and the information from the sampling plan to determine the lot decision.
Note
For variables sampling plans, you can examine only one measurement per sampling plan. For example, if you need to inspect for wafer thickness and wafer width, you need two separate sampling plans.
The manufacturer will accept the lot if it meets the following three conditions:
Standard deviation is less than the maximum standard deviation.
Z.LSL is greater than or equal to the critical distance.
Z.USL is greater than or equal to the critical distance.
Acceptance Sampling by Variables - Accept/Reject Lot
Make Accept or Reject Decision Using Thickness
Sample Size 259
Mean 0.403108
Standard Deviation 0.0469204
Lower Specification Limit (LSL) 0.395
Upper Specification Limit (USL) 0.415
Z.LSL 0.172803
Z.USL 0.253452
Critical Distance (k Value) 3.44914
Maximum Standard Deviation (MSD) 0.0027533
Decision: Reject lot.
Key Results: Z.LSL, Z.USL, Critical Distance, Maximum Standard Deviation, Decision
In these results, the standard deviation is greater than the maximum standard deviation. The Z.LSL and Z.USL values are less than the critical distance. The manufacturer rejects the lot.
