Appeal No. 1998-3339 Page 2
Application No. 08/614,459
the first step to ensure that procedures, especially new ones,
are not adversely affecting the overall output.
Previously known procedures for reject analysis were
effectively based on univariate statistical process control
(SPC) techniques. These techniques were not suitable for use
with complex processes where, for each process, many variables
are monitored to assess the status of the process. Some of
the variables in such a process may not be independent, and
the degree to which the variables are correlated is often
unknown, making it difficult to assess the status of the
process.
The appellants’ method for reject analysis applies
multivariate statistical process control techniques. The
method allows rejects from a process to be controlled simply
and effectively by deriving a Hotelling’s T statistic for a2
series of variables or classification categories that impact
reject performance characteristics. The calculated T value2
is compared with a standard value for the particular system.
If the value exceeds the critical value, it suggests that
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