WTADJX Is Coming: Calibration Weighting in SUDAAN when Unit Nonrespondents Are Not Missing at Random and Other Applications
Kott, P. S. (2011, July). WTADJX Is Coming: Calibration Weighting in SUDAAN when Unit Nonrespondents Are Not Missing at Random and Other Applications. Presented at JSM 2011, Miami Beach, FL.
RTI's SUDAAN 11 will include a new weight calibration procedure, WTADJX, which will allow the set of model variables governing the response model to differ from the set of benchmark variables. As a result, the new procedure may be used to assess and perhaps even correct for unit nonresponse that is not missing at random; in other words, when unit response is a function of variables known only for the respondents. The WTADJUST procedure, introduced in SUDAAN 10, produces calibrated weights by implementing an extension of generalized raking. By forcing the weighted totals for a set of "calibration variables" to equal benchmark totals computed from either the whole sample, a larger sample, or the entire population, WTADUST-produced calibration weights can reduce or eliminate the potential for bias from unit nonresponse under a reasonable response model. With WTADJX, the response-model and the benchmark variables will be allowed to differ. Other potential uses of this procedure include producing well-behaved calibrated weights asymptotically identical to "optimal" ones and simplifying the computation of replicate weights when using WTADJUST to produce calibration weights.