>>>>>>>> SAS Notes -- Copyright (c) 1991 - 2000 by SAS Institute Inc. <<<<<<<<
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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