The DISTANCE Procedure
Since variables with large variances tend to have more effect on the proximity measure than those with small variances, it is recommended that you standardize the variables before the computation of the proximity measure. The DISTANCE procedure provides a convenient way to standardize each variable with its own method before the proximity measures are computed. You can also perform the standardization by using the STDIZE procedure, with the limitation that all variables must be standardized with the same method.
Variable standardization is not required if any of the following conditions is true:
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if there is only one level of measurement
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if only asymmetric nominal and nominal levels are specified
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if the NOSTD option is specified in the PROC DISTANCE statement
Otherwise, standardization is mandatory.
When standardization is mandatory and no standardization method is specified, a default method of standardization will be used. This default method is determined by the measurement level. In general, the default method is STD for interval variables and is MAXABS for ratio variables except when METHOD=GOWER or METHOD=DGOWER is specified. See the STD= option in the section VAR Statement for the default methods for GOWER and DGOWER as well as methods available for standardizing variables.
When standardization is mandatory, PROC DISTANCE ignores the REPONLY option, if it is specified.