Ansi Z.4

ANSI Z1.4 for Defects Per Unit The ANSI Z1.4 standard can be used to inspect for both defective units and defects per unit. It was based on and is nearly identical to MIL-STD-105E which has been obsoleted. Characteristic: Defects per Unit Parameters: AQL = 0.010 defects per 100 units, ..., 1000 defects per 100 units. Level Of Inspection = S1, S2, S3, S4, L-I, L-II and L-III Lot Size = from 2 on up Type = single, double and multiple Options = normal, tightened, reduced, full switching, full switching without limit numbers, switching without reduced inspection Procedure: For a given AQL, level of inspection, lot size and type, the standard gives three plans called normal, tightened and reduced. You can select an individual sampling plan from the standard and evaluate it. The standard also contains a set of rules for switching between these plans. The standard intends that these switching rules be used. You can also evaluate the combined protection obtained using these switching rules. The switching rules work as follows: Start: Start using the normal sampling plan. N to T: If, while on normal inspection, 2 of 5 consecutive lots are rejected, switch to the tightened plan. N to R: If, while on normal inspection, 10 consecutive lots are accepted and the total number of defects in these 10 samples does not exceed a limit number, switch to the reduced plan. This rule can change somewhat for smaller sample sizes. T to N: If, while on tightened inspection, 5 consecutive lots are accepted, switch to the normal plan. R to N: If, while on reduced inspection, more than a specified number of defects are found in a sample, switch to the normal plan. The switching rules have two options, the limit numbers for switching from normal to reduced are optional and the use of the reduced sampling plan is optional. The exact rules are displayed in the ANSI Z1.4 for Defects Per Unit dialog box once you have selected the plan. Assumptions: (1) Representative sample (2) If the switching rules are used, it is assumed that one is inspecting a series lots.