When the following conditions are met in the SURVEYREG procedure:

• the REF= option is specified for a variable in the CLASS statement
• the SOLUTION option is specified in the MODEL statement
• the jackknife method of variance estimation is used

the standard errors and related statistics for the estimated regression coefficients of effects involving the class variable are incorrect.

The VARMETHOD=JACKKNIFE or JK option in the PROC SURVEYREG statement specifies the delete-1 jackknife method. If you provide replicate weights with a REPWEIGHTS statement, VARMETHOD=JACKKNIFE is the default variance estimation method.

To circumvent the problem, do not use the REF= option. Refer to KB0057269: "Setting the reference levels for the CLASS predictor variables" for alternative approaches to ordering class variable levels.