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The SHEWHART Procedure |
You can use the PCTLDEF= option to specify one of five definitions for computing quantile statistics (percentiles). Let equal the number of nonmissing values for a variable, and let
represent the ordered values of the process variable. For the
th percentile, set
, and express
as
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where is the integer part of
, and
is the fractional part of
.
The th percentile (call it
) can be defined in five ways, as described in the next five sections.
This uses the weighted average at
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where is taken to be
.
This uses the observation numbered closest to
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where is the integer part of
.
This uses the empirical distribution function
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This uses the weighted average aimed at
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where , and where
is taken to be
.
This uses the empirical distribution function with averaging
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