Acceptance Sampling by Variables - Accept/Reject

Calculated Criteria - Decision

  

If the Zs are greater than the critical distance, and if the standard deviation is less than the maximum standard deviation (MSD), accept the entire lot. Otherwise, reject it.

Example Output

Z.LSL                             0.172803

Z.USL                             0.253452

Critical Distance (k Value)       3.44914

Maximum Standard Deviation (MSD)  0.0027533

 

Decision:  Reject lot.

Interpretation

For each lot of 3,600 camera lenses, you need to randomly select and measure the thickness of 259 of them. From these measurements, Minitab determines the mean and standard deviation to calculate the Z values:

·    Z.LSL = (mean - lower spec) / standard deviation = 0.172803

·    Z.USL = (upper spec - mean) / standard deviation = 0.253452

The Zs are less than the critical distance (3.44914), and the standard deviation (0.0469204) is greater than the MSD (0.0027533). Therefore, you must reject the entire lot (Reject lot) of lenses.