SAS Note V6-SHEWHART-G774

From: tsdlist@unx.sas.com
Date: Mon Aug 21 2000 - 13:55:58 EDT

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    V6-SHEWHART-G774 *** ALERT NOTE *** PRODUCT: QC

    TITLE: Tests may be incorrect for P and NP charts with TESTNMETHOD=STANDARDIZE

    KEYS: INCORRSTAT INCORROUT TESTS= TESTS FOR SPECIAL CAUSES PCHART NPCHART P
           NP OUTTABLE= WRONG SIGNAL FLAG TESTNMETHOD= STANDARDIZE

        In PROC SHEWHART, when the TESTNMETHOD=STANDARDIZE option is used on a
        PCHART or NPCHART statement and the TESTS= option is specified, the
        resulting positive test signals may be incorrect and positive tests may
        not be flagged. This problem can occur when the computed upper control
        limit for any subgroup exceeds 1 in P charts, or exceeds the subgroup
        sample size in NP charts. When this happens for the given chart type,
        subgroup i may be be incorrectly included or omitted from contributing
        to a positive test run. Both the printed plot and the OUTTABLE= data
        set will contain the wrong results. There is no way to tell when false
        positive or false negative signals have occurred as this will be
        data-dependent.

        For P and NP charts, if the computed upper control limit does not exceed
        1 or the subgroup sample size respectively for any subgroup, then all
        tests flags will be correct.

        There is no circumvention for this problem. The standardized values
        could be computed in a DATA step and the tests manually applied. See
        http://www.sas.com/service/techsup/unotes/SN/002/002705.html for a
        description of computing the standardized values.

    +------REPORTED------+ +---FIXED---+
    SYSTEM RELEASE LEVEL RELEASE LEVEL

    IABI 6.10 TS018 8.00
    MIPS ABI 6.10 TS018 8.00
    Macintosh 6.10 TS037
    OSF/AXP 6.10 TS018
    OS/2 6.10 TS019 8.00
    Windows 6.10 TS019
    AIX/R 6.11 TS020 8.00
    HP800 6.11 TS020 8.00
    Solaris 6.11 TS020 8.00
    WIN/NT 6.11 TS040 8.00
    Win95 6.11 TS040 8.00
    DigitUnx 6.12 TS040 8.00
    VMS/AXP 6.12 TS020 8.00



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