Survey Methodology
Dealing with undercoverage for non-probability survey samples

by Yilin Chen, Pengfei Li and Changbao WuNote 1

  • Release date: January 3, 2024

Abstract

Population undercoverage is one of the main hurdles faced by statistical analysis with non-probability survey samples. We discuss two typical scenarios of undercoverage, namely, stochastic undercoverage and deterministic undercoverage. We argue that existing estimation methods under the positivity assumption on the propensity scores (i.e., the participation probabilities) can be directly applied to handle the scenario of stochastic undercoverage. We explore strategies for mitigating biases in estimating the mean of the target population under deterministic undercoverage. In particular, we examine a split population approach based on a convex hull formulation, and construct estimators with reduced biases. A doubly robust estimator can be constructed if a followup subsample of the reference probability survey with measurements on the study variable becomes feasible. Performances of six competing estimators are investigated through a simulation study and issues which require further investigation are briefly discussed.

Key Words: Auxiliary information; Calibration method; Convex hull; Doubly robust estimator; Inverse probability weighting; Model-based prediction; Outcome regression; Propensity score; Split population.

Table of contents

How to cite

Chen, Y., Li, P. and Wu, C. (2023). Dealing with undercoverage for non-probability survey samples. Survey Methodology, Statistics Canada, Catalogue No. 12‑001‑X, Vol. 49, No. 2. Paper available at http://www.statcan.gc.ca/pub/12-001-x/2023002/article/00005-eng.htm.

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