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Attribute Inspection / ANSI Z1.4 / MIL Std 105E

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  • #46207

    Lee
    Participant

    I need some input if I am using the Subject standard correctly, in particular about the risk of acceptance.
    Taking one specific:
    For the normal inspection of a lot of 51-90 items, from Table I I one would select sample plan E.  From Table II-A, I understand that I should draw 13 samples for that sample plan.  For an AQL=10, if 4 or more of the samples are non-conforming then that lot should be labeled “to not accept” ( ANSI Std. Z1.4, Section 6.1 phrase).
    Assuming the above is correct, on to my question of risk. Lets assume that I had 75 items in the particular lot I’m working with (fits sample plan E), and 8 of the 13 samples were nonconforming.  8/75=10.6% non-conforming in that lot.  Is it correct to Use Table X-E-1, use the column for AQL=1, p (in percent nonconforming), read down to the nearest value 11.3%, and then go to the left column and conclude that on the average Pa=95%, i.e., that in the future I should expect that about 95% of the future lots would meet the acceptance criteria (have three or fewer defects)?
    I suspect that being new to the Standard that I have more that one error  in the above, so I’m asking for assistance before I apply this to a “real” case.  Thanks for the help.
    Eugene

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    #152462

    Lee
    Participant

    In my late Fri post it was not obvious (at least to me, on a Monday morning) as to what I was trying to accomplish.  We are using the ANSI Std to determine a “good” sample size for our lots, the lots vary in size from <10 to about 500.  The sample testing is to be determined if we "have a problem".  That implies that we set an AQL, but to do that I need to get the AQL in terms of the probability of future testing being satisfied, as that is closer to the terms/way-of-thinking that is used here.  The example provided was to see of I was handing the ANSI tables correctly.
    Thanks

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