![IconGems-Print](images/IconGems-Print.png)
126 – 126 - Interpreting Nonprobability Samples: Discoveries and Challenges
Creating Statistically-Defensible Calibrated Weights for a Blended Sample and Measuring the Accuracy of the Resulting Estimates
Phillip S. Kott
RTI International
We show how calibration weighting can be employed to combine a probability and a nonprobability sample of the same population in a statistically-defensible manner. This is done by assuming the probability of a population element being included in the nonprobability sample can be modeled as a logit function of variables known for all members of both samples. Estimating these probabilities for the members of the nonprobability sample with a calibration equation and treating their inverses as quasi-probability weights is a key to creating composite weights for the blended sample. The WTADJX procedure in SUDAAN® is employed to generate those weights and then measure the standard errors or resulting estimated means and totals.